diff --git a/crossbeam-channel/tests/after.rs b/crossbeam-channel/tests/after.rs
index 20670dc5a..7756a4486 100644
--- a/crossbeam-channel/tests/after.rs
+++ b/crossbeam-channel/tests/after.rs
@@ -1,4 +1,5 @@
 //! Tests for the after channel flavor.
+#![cfg(not(miri))] // todo
 
 use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering;
diff --git a/crossbeam-channel/tests/array.rs b/crossbeam-channel/tests/array.rs
index a7ae323d9..4d682a10a 100644
--- a/crossbeam-channel/tests/array.rs
+++ b/crossbeam-channel/tests/array.rs
@@ -1,4 +1,5 @@
 //! Tests for the array channel flavor.
+#![cfg(not(miri))] // todo
 
 use std::any::Any;
 use std::sync::atomic::AtomicUsize;
diff --git a/crossbeam-channel/tests/golang.rs b/crossbeam-channel/tests/golang.rs
index 69a9315a0..daaa241f4 100644
--- a/crossbeam-channel/tests/golang.rs
+++ b/crossbeam-channel/tests/golang.rs
@@ -9,6 +9,8 @@
 //!   - https://golang.org/LICENSE
 //!   - https://golang.org/PATENTS
 
+#![cfg(not(miri))] // todo
+
 use std::alloc::{GlobalAlloc, Layout, System};
 use std::any::Any;
 use std::cell::Cell;
diff --git a/crossbeam-channel/tests/iter.rs b/crossbeam-channel/tests/iter.rs
index 38bcac2f0..7fdbde9da 100644
--- a/crossbeam-channel/tests/iter.rs
+++ b/crossbeam-channel/tests/iter.rs
@@ -54,6 +54,7 @@ fn recv_iter_break() {
     .unwrap();
 }
 
+#[cfg_attr(miri, ignore)] // todo
 #[test]
 fn recv_try_iter() {
     let (request_s, request_r) = unbounded();
diff --git a/crossbeam-channel/tests/list.rs b/crossbeam-channel/tests/list.rs
index 8b8410540..5d9b926b2 100644
--- a/crossbeam-channel/tests/list.rs
+++ b/crossbeam-channel/tests/list.rs
@@ -239,6 +239,9 @@ fn disconnect_wakes_receiver() {
 
 #[test]
 fn spsc() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 100_000;
 
     let (s, r) = unbounded();
@@ -261,6 +264,9 @@ fn spsc() {
 
 #[test]
 fn mpmc() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 25_000;
     const THREADS: usize = 4;
 
@@ -295,6 +301,9 @@ fn mpmc() {
 
 #[test]
 fn stress_oneshot() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     for _ in 0..COUNT {
@@ -308,6 +317,7 @@ fn stress_oneshot() {
     }
 }
 
+#[cfg_attr(miri, ignore)] // todo
 #[test]
 fn stress_iter() {
     const COUNT: usize = 100_000;
@@ -371,6 +381,7 @@ fn stress_timeout_two_threads() {
     .unwrap();
 }
 
+#[cfg_attr(miri, ignore)] // todo
 #[test]
 fn drops() {
     static DROPS: AtomicUsize = AtomicUsize::new(0);
@@ -421,6 +432,9 @@ fn drops() {
 
 #[test]
 fn linearizable() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 25_000;
     const THREADS: usize = 4;
 
@@ -441,6 +455,9 @@ fn linearizable() {
 
 #[test]
 fn fairness() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = unbounded::<()>();
@@ -463,6 +480,9 @@ fn fairness() {
 
 #[test]
 fn fairness_duplicates() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s, r) = unbounded();
diff --git a/crossbeam-channel/tests/mpsc.rs b/crossbeam-channel/tests/mpsc.rs
index 2a0786a71..b07144e58 100644
--- a/crossbeam-channel/tests/mpsc.rs
+++ b/crossbeam-channel/tests/mpsc.rs
@@ -264,6 +264,7 @@ mod channel_tests {
         assert!(tx2.send(1).is_err());
     }
 
+    #[cfg_attr(miri, ignore)] //todo
     #[test]
     fn port_gone_concurrent() {
         let (tx, rx) = channel::<i32>();
@@ -274,6 +275,7 @@ mod channel_tests {
         t.join().unwrap();
     }
 
+    #[cfg_attr(miri, ignore)] //todo
     #[test]
     fn port_gone_concurrent_shared() {
         let (tx, rx) = channel::<i32>();
@@ -314,13 +316,18 @@ mod channel_tests {
 
     #[test]
     fn stress() {
+        #[cfg(miri)]
+        const COUNT: usize = 500;
+        #[cfg(not(miri))]
+        const COUNT: usize = 10000;
+
         let (tx, rx) = channel::<i32>();
         let t = thread::spawn(move || {
-            for _ in 0..10000 {
+            for _ in 0..COUNT {
                 tx.send(1).unwrap();
             }
         });
-        for _ in 0..10000 {
+        for _ in 0..COUNT {
             assert_eq!(rx.recv().unwrap(), 1);
         }
         t.join().ok().unwrap();
@@ -328,6 +335,9 @@ mod channel_tests {
 
     #[test]
     fn stress_shared() {
+        #[cfg(miri)]
+        const AMT: u32 = 500;
+        #[cfg(not(miri))]
         const AMT: u32 = 10000;
         const NTHREADS: u32 = 8;
         let (tx, rx) = channel::<i32>();
@@ -735,12 +745,16 @@ mod channel_tests {
 
     #[test]
     fn recv_a_lot() {
+        #[cfg(miri)]
+        const COUNT: usize = 500;
+        #[cfg(not(miri))]
+        const COUNT: usize = 10000;
         // Regression test that we don't run out of stack in scheduler context
         let (tx, rx) = channel();
-        for _ in 0..10000 {
+        for _ in 0..COUNT {
             tx.send(()).unwrap();
         }
-        for _ in 0..10000 {
+        for _ in 0..COUNT {
             rx.recv().unwrap();
         }
     }
@@ -841,6 +855,7 @@ mod channel_tests {
         t.join().unwrap();
     }
 
+    #[cfg_attr(miri, ignore)]
     #[test]
     fn test_recv_try_iter() {
         let (request_tx, request_rx) = channel();
@@ -955,6 +970,7 @@ mod channel_tests {
 }
 
 // Source: https://github.com/rust-lang/rust/blob/master/src/libstd/sync/mpsc/mod.rs
+#[cfg(not(miri))] // unsupported operation: the main thread terminated without waiting for other threads
 mod sync_channel_tests {
     use super::*;
 
@@ -1079,13 +1095,15 @@ mod sync_channel_tests {
 
     #[test]
     fn stress() {
+        const COUNT: usize = 10000;
+
         let (tx, rx) = sync_channel::<i32>(0);
         let t = thread::spawn(move || {
-            for _ in 0..10000 {
+            for _ in 0..COUNT {
                 tx.send(1).unwrap();
             }
         });
-        for _ in 0..10000 {
+        for _ in 0..COUNT {
             assert_eq!(rx.recv().unwrap(), 1);
         }
         t.join().unwrap();
@@ -1093,10 +1111,12 @@ mod sync_channel_tests {
 
     #[test]
     fn stress_recv_timeout_two_threads() {
+        const COUNT: usize = 10000;
+
         let (tx, rx) = sync_channel::<i32>(0);
 
         let t = thread::spawn(move || {
-            for _ in 0..10000 {
+            for _ in 0..COUNT {
                 tx.send(1).unwrap();
             }
         });
@@ -1113,7 +1133,7 @@ mod sync_channel_tests {
             }
         }
 
-        assert_eq!(recv_count, 10000);
+        assert_eq!(recv_count, COUNT);
         t.join().unwrap();
     }
 
@@ -1449,12 +1469,14 @@ mod sync_channel_tests {
 
     #[test]
     fn recv_a_lot() {
+        const COUNT: usize = 10000;
+
         // Regression test that we don't run out of stack in scheduler context
-        let (tx, rx) = sync_channel(10000);
-        for _ in 0..10000 {
+        let (tx, rx) = sync_channel(COUNT);
+        for _ in 0..COUNT {
             tx.send(()).unwrap();
         }
-        for _ in 0..10000 {
+        for _ in 0..COUNT {
             rx.recv().unwrap();
         }
     }
@@ -1792,6 +1814,9 @@ mod select_tests {
 
     #[test]
     fn stress() {
+        #[cfg(miri)]
+        const AMT: i32 = 500;
+        #[cfg(not(miri))]
         const AMT: i32 = 10000;
         let (tx1, rx1) = channel::<i32>();
         let (tx2, rx2) = channel::<i32>();
diff --git a/crossbeam-channel/tests/ready.rs b/crossbeam-channel/tests/ready.rs
index 700f487e0..19a1fe31f 100644
--- a/crossbeam-channel/tests/ready.rs
+++ b/crossbeam-channel/tests/ready.rs
@@ -490,6 +490,9 @@ fn nesting() {
 
 #[test]
 fn stress_recv() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = unbounded();
@@ -527,6 +530,9 @@ fn stress_recv() {
 
 #[test]
 fn stress_send() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded(0);
@@ -561,6 +567,9 @@ fn stress_send() {
 
 #[test]
 fn stress_mixed() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded(0);
@@ -724,6 +733,9 @@ fn channel_through_channel() {
 
 #[test]
 fn fairness1() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded::<()>(COUNT);
@@ -769,6 +781,9 @@ fn fairness1() {
 
 #[test]
 fn fairness2() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 100_000;
 
     let (s1, r1) = unbounded::<()>();
diff --git a/crossbeam-channel/tests/select.rs b/crossbeam-channel/tests/select.rs
index 4cf08b6a6..51f8ea558 100644
--- a/crossbeam-channel/tests/select.rs
+++ b/crossbeam-channel/tests/select.rs
@@ -406,6 +406,7 @@ fn both_ready() {
     .unwrap();
 }
 
+#[cfg_attr(miri, ignore)]
 #[test]
 fn loop_try() {
     const RUNS: usize = 20;
@@ -690,6 +691,9 @@ fn nesting() {
 
 #[test]
 fn stress_recv() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = unbounded();
@@ -728,6 +732,9 @@ fn stress_recv() {
 
 #[test]
 fn stress_send() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded(0);
@@ -763,6 +770,9 @@ fn stress_send() {
 
 #[test]
 fn stress_mixed() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded(0);
@@ -1000,6 +1010,9 @@ fn channel_through_channel() {
 
 #[test]
 fn linearizable_try() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 100_000;
 
     for step in 0..2 {
@@ -1052,6 +1065,9 @@ fn linearizable_try() {
 
 #[test]
 fn linearizable_timeout() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 100_000;
 
     for step in 0..2 {
@@ -1104,6 +1120,9 @@ fn linearizable_timeout() {
 
 #[test]
 fn fairness1() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded::<()>(COUNT);
@@ -1150,6 +1169,9 @@ fn fairness1() {
 
 #[test]
 fn fairness2() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = unbounded::<()>();
@@ -1266,6 +1288,9 @@ fn send_and_clone() {
 
 #[test]
 fn reuse() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded(0);
diff --git a/crossbeam-channel/tests/select_macro.rs b/crossbeam-channel/tests/select_macro.rs
index c05f7a0e6..a9e0604c0 100644
--- a/crossbeam-channel/tests/select_macro.rs
+++ b/crossbeam-channel/tests/select_macro.rs
@@ -283,6 +283,7 @@ fn both_ready() {
     .unwrap();
 }
 
+#[cfg_attr(miri, ignore)]
 #[test]
 fn loop_try() {
     const RUNS: usize = 20;
@@ -485,6 +486,9 @@ fn panic_receiver() {
 
 #[test]
 fn stress_recv() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = unbounded();
@@ -518,6 +522,9 @@ fn stress_recv() {
 
 #[test]
 fn stress_send() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded(0);
@@ -548,6 +555,9 @@ fn stress_send() {
 
 #[test]
 fn stress_mixed() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded(0);
@@ -726,6 +736,9 @@ fn channel_through_channel() {
 
 #[test]
 fn linearizable_default() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 100_000;
 
     for step in 0..2 {
@@ -770,6 +783,9 @@ fn linearizable_default() {
 
 #[test]
 fn linearizable_timeout() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 100_000;
 
     for step in 0..2 {
@@ -814,6 +830,9 @@ fn linearizable_timeout() {
 
 #[test]
 fn fairness1() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded::<()>(COUNT);
@@ -838,6 +857,9 @@ fn fairness1() {
 
 #[test]
 fn fairness2() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = unbounded::<()>();
@@ -875,6 +897,9 @@ fn fairness2() {
 
 #[test]
 fn fairness_recv() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded::<()>(COUNT);
@@ -897,6 +922,9 @@ fn fairness_recv() {
 
 #[test]
 fn fairness_send() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, _r1) = bounded::<()>(COUNT);
diff --git a/crossbeam-channel/tests/tick.rs b/crossbeam-channel/tests/tick.rs
index 5dc87306f..3d3eee790 100644
--- a/crossbeam-channel/tests/tick.rs
+++ b/crossbeam-channel/tests/tick.rs
@@ -1,4 +1,5 @@
 //! Tests for the tick channel flavor.
+#![cfg(not(miri))]
 
 use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering;
diff --git a/crossbeam-channel/tests/zero.rs b/crossbeam-channel/tests/zero.rs
index 66dcc1eeb..baea5e8ed 100644
--- a/crossbeam-channel/tests/zero.rs
+++ b/crossbeam-channel/tests/zero.rs
@@ -187,6 +187,9 @@ fn send_timeout() {
 
 #[test]
 fn len() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 25_000;
 
     let (s, r) = bounded(0);
@@ -249,6 +252,9 @@ fn disconnect_wakes_receiver() {
 
 #[test]
 fn spsc() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 100_000;
 
     let (s, r) = bounded(0);
@@ -271,6 +277,9 @@ fn spsc() {
 
 #[test]
 fn mpmc() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 25_000;
     const THREADS: usize = 4;
 
@@ -303,6 +312,9 @@ fn mpmc() {
 
 #[test]
 fn stress_oneshot() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     for _ in 0..COUNT {
@@ -316,6 +328,7 @@ fn stress_oneshot() {
     }
 }
 
+#[cfg_attr(miri, ignore)]
 #[test]
 fn stress_iter() {
     const COUNT: usize = 1000;
@@ -383,6 +396,7 @@ fn stress_timeout_two_threads() {
     .unwrap();
 }
 
+#[cfg_attr(miri, ignore)]
 #[test]
 fn drops() {
     static DROPS: AtomicUsize = AtomicUsize::new(0);
@@ -428,6 +442,9 @@ fn drops() {
 
 #[test]
 fn fairness() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s1, r1) = bounded::<()>(0);
@@ -459,6 +476,9 @@ fn fairness() {
 
 #[test]
 fn fairness_duplicates() {
+    #[cfg(miri)]
+    const COUNT: usize = 500;
+    #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 
     let (s, r) = bounded::<()>(0);