diff --git a/lib/_inspect.js b/lib/_inspect.js
index ac32e0a..d3d28d5 100644
--- a/lib/_inspect.js
+++ b/lib/_inspect.js
@@ -53,53 +53,6 @@ function getDefaultPort() {
   return 9229;
 }
 
-function runScript(script, scriptArgs, inspectPort, childPrint) {
-  return new Promise((resolve) => {
-    const args = [
-      '--inspect',
-      `--debug-brk=${inspectPort}`,
-    ].concat([script], scriptArgs);
-    const child = spawn(process.execPath, args);
-    child.stdout.setEncoding('utf8');
-    child.stderr.setEncoding('utf8');
-    child.stdout.on('data', childPrint);
-    child.stderr.on('data', childPrint);
-
-    let output = '';
-    function waitForListenHint(text) {
-      output += text;
-      if (/chrome-devtools:\/\//.test(output)) {
-        child.stderr.removeListener('data', waitForListenHint);
-        resolve(child);
-      }
-    }
-
-    child.stderr.on('data', waitForListenHint);
-  });
-}
-
-function createAgentProxy(domain, client) {
-  const agent = new EventEmitter();
-  agent.then = (...args) => {
-    // TODO: potentially fetch the protocol and pretty-print it here.
-    const descriptor = {
-      [util.inspect.custom](depth, { stylize }) {
-        return stylize(`[Agent ${domain}]`, 'special');
-      },
-    };
-    return Promise.resolve(descriptor).then(...args);
-  };
-
-  return new Proxy(agent, {
-    get(target, name) {
-      if (name in target) return target[name];
-      return function callVirtualMethod(params) {
-        return client.callMethod(`${domain}.${name}`, params);
-      };
-    },
-  });
-}
-
 function portIsFree(host, port, timeout = 2000) {
   const retryDelay = 150;
   let didTimeOut = false;
@@ -139,6 +92,56 @@ function portIsFree(host, port, timeout = 2000) {
   });
 }
 
+function runScript(script, scriptArgs, inspectHost, inspectPort, childPrint) {
+  return portIsFree(inspectHost, inspectPort)
+    .then(() => {
+      return new Promise((resolve) => {
+        const args = [
+          '--inspect',
+          `--debug-brk=${inspectPort}`,
+        ].concat([script], scriptArgs);
+        const child = spawn(process.execPath, args);
+        child.stdout.setEncoding('utf8');
+        child.stderr.setEncoding('utf8');
+        child.stdout.on('data', childPrint);
+        child.stderr.on('data', childPrint);
+
+        let output = '';
+        function waitForListenHint(text) {
+          output += text;
+          if (/chrome-devtools:\/\//.test(output)) {
+            child.stderr.removeListener('data', waitForListenHint);
+            resolve(child);
+          }
+        }
+
+        child.stderr.on('data', waitForListenHint);
+      });
+    });
+}
+
+function createAgentProxy(domain, client) {
+  const agent = new EventEmitter();
+  agent.then = (...args) => {
+    // TODO: potentially fetch the protocol and pretty-print it here.
+    const descriptor = {
+      [util.inspect.custom](depth, { stylize }) {
+        return stylize(`[Agent ${domain}]`, 'special');
+      },
+    };
+    return Promise.resolve(descriptor).then(...args);
+  };
+
+  return new Proxy(agent, {
+    get(target, name) {
+      if (name in target) return target[name];
+      return function callVirtualMethod(params) {
+        return client.callMethod(`${domain}.${name}`, params);
+      };
+    },
+  });
+}
+
 class NodeInspector {
   constructor(options, stdin, stdout) {
     this.options = options;
@@ -152,6 +155,7 @@ class NodeInspector {
       this._runScript = runScript.bind(null,
                                        options.script,
                                        options.scriptArgs,
+                                       options.host,
                                        options.port,
                                        this.childPrint.bind(this));
     } else {
@@ -220,12 +224,7 @@ class NodeInspector {
     this.killChild();
     const { host, port } = this.options;
 
-    const runOncePortIsFree = () => {
-      return portIsFree(host, port)
-        .then(() => this._runScript());
-    };
-
-    return runOncePortIsFree().then((child) => {
+    return this._runScript().then((child) => {
       this.child = child;
 
       let connectionAttempts = 0;
@@ -308,6 +307,22 @@ function parseArgv([target, ...args]) {
     port = parseInt(portMatch[1], 10);
     script = args[0];
     scriptArgs = args.slice(1);
+  } else if (args.length === 1 && /^\d+$/.test(args[0]) && target === '-p') {
+    // Start debugger against a given pid
+    const pid = parseInt(args[0], 10);
+    try {
+      process._debugProcess(pid);
+    } catch (e) {
+      if (e.code === 'ESRCH') {
+        /* eslint-disable no-console */
+        console.error(`Target process: ${pid} doesn't exist.`);
+        /* eslint-enable no-console */
+        process.exit(1);
+      }
+      throw e;
+    }
+    script = null;
+    isRemote = true;
   }
 
   return {
diff --git a/test/cli/pid.test.js b/test/cli/pid.test.js
new file mode 100644
index 0000000..15d7fde
--- /dev/null
+++ b/test/cli/pid.test.js
@@ -0,0 +1,52 @@
+'use strict';
+const { spawn } = require('child_process');
+const Path = require('path');
+
+const { test } = require('tap');
+
+const startCLI = require('./start-cli');
+
+function launchTarget(...args) {
+  const childProc = spawn(process.execPath, args);
+  return Promise.resolve(childProc);
+}
+
+// process.debugPort is our proxy for "the version of node used to run this
+// test suite doesn't support SIGUSR1 for enabling --inspect for a process".
+const defaultsToOldProtocol = process.debugPort === 5858;
+
+test('examples/alive.js', { skip: defaultsToOldProtocol }, (t) => {
+  const script = Path.join('examples', 'alive.js');
+  let cli = null;
+  let target = null;
+
+  function cleanup(error) {
+    if (cli) {
+      cli.quit();
+      cli = null;
+    }
+    if (target) {
+      target.kill();
+      target = null;
+    }
+    if (error) throw error;
+  }
+
+  return launchTarget(script)
+    .then((childProc) => {
+      target = childProc;
+      cli = startCLI(['-p', `${target.pid}`]);
+      return cli.waitForPrompt();
+    })
+    .then(() => cli.command('sb("alive.js", 3)'))
+    .then(() => cli.waitFor(/break/))
+    .then(() => cli.waitForPrompt())
+    .then(() => {
+      t.match(
+        cli.output,
+        '> 3   ++x;',
+        'marks the 3rd line');
+    })
+    .then(() => cleanup())
+    .then(null, cleanup);
+});