diff --git a/Python/thread.c b/Python/thread.c
index c9356dc..bc501822 100644
--- a/Python/thread.c
+++ b/Python/thread.c
@@ -95,6 +95,11 @@
 	PyThread__init_thread();
 }
 
+/* Support for runtime thread stack size tuning.
+   A value of 0 means using the platform's default stack size
+   or the size specified by the THREAD_STACK_SIZE macro. */
+static size_t _pythread_stacksize = 0;
+
 #ifdef SGI_THREADS
 #include "thread_sgi.h"
 #endif
@@ -150,6 +155,28 @@
 #endif
 */
 
+/* return the current thread stack size */
+size_t
+PyThread_get_stacksize(void)
+{
+	return _pythread_stacksize;
+}
+
+/* Only platforms defining a THREAD_SET_STACKSIZE() macro
+   in thread_<platform>.h support changing the stack size.
+   Return 0 if stack size is valid,
+          -1 if stack size value is invalid,
+          -2 if setting stack size is not supported. */
+int
+PyThread_set_stacksize(size_t size)
+{
+#if defined(THREAD_SET_STACKSIZE)
+	return THREAD_SET_STACKSIZE(size);
+#else
+	return -2;
+#endif
+}
+
 #ifndef Py_HAVE_NATIVE_TLS
 /* If the platform has not supplied a platform specific
    TLS implementation, provide our own.
diff --git a/Python/thread_nt.h b/Python/thread_nt.h
index 4dc6d6c..67f5ed5 100644
--- a/Python/thread_nt.h
+++ b/Python/thread_nt.h
@@ -196,7 +196,7 @@
 	if (obj.done == NULL)
 		return -1;
 
-	rv = _beginthread(bootstrap, 0, &obj); /* use default stack size */
+	rv = _beginthread(bootstrap, _pythread_stacksize, &obj);
 	if (rv == (Py_uintptr_t)-1) {
 		/* I've seen errno == EAGAIN here, which means "there are
 		 * too many threads".
@@ -335,3 +335,30 @@
 	if (!(aLock && LeaveNonRecursiveMutex((PNRMUTEX) aLock)))
 		dprintf(("%ld: Could not PyThread_release_lock(%p) error: %l\n", PyThread_get_thread_ident(), aLock, GetLastError()));
 }
+
+/* minimum/maximum thread stack sizes supported */
+#define THREAD_MIN_STACKSIZE	0x8000		/* 32kB */
+#define THREAD_MAX_STACKSIZE	0x10000000	/* 256MB */
+
+/* set the thread stack size.
+ * Return 0 if size is valid, -1 otherwise.
+ */
+static int
+_pythread_nt_set_stacksize(size_t size)
+{
+	/* set to default */
+	if (size == 0) {
+		_pythread_stacksize = 0;
+		return 0;
+	}
+
+	/* valid range? */
+	if (size >= THREAD_MIN_STACKSIZE && size < THREAD_MAX_STACKSIZE) {
+		_pythread_stacksize = size;
+		return 0;
+	}
+
+	return -1;
+}
+
+#define THREAD_SET_STACKSIZE(x)	_pythread_nt_set_stacksize(x)
diff --git a/Python/thread_os2.h b/Python/thread_os2.h
index 86e91c1..3ed9d08 100644
--- a/Python/thread_os2.h
+++ b/Python/thread_os2.h
@@ -14,10 +14,13 @@
 long PyThread_get_thread_ident(void);
 #endif
 
+/* default thread stack size of 64kB */
 #if !defined(THREAD_STACK_SIZE)
 #define	THREAD_STACK_SIZE	0x10000
 #endif
 
+#define OS2_STACKSIZE(x)	(x ? x : THREAD_STACK_SIZE)
+
 /*
  * Initialization of the C package, should not be needed.
  */
@@ -35,7 +38,10 @@
 	int aThread;
 	int success = 0;
 
-	aThread = _beginthread(func, NULL, THREAD_STACK_SIZE, arg);
+	aThread = _beginthread(func,
+				NULL,
+				OS2_STACKSIZE(_pythread_stacksize),
+				arg);
 
 	if (aThread == -1) {
 		success = -1;
@@ -275,3 +281,30 @@
 	DosExitCritSec();
 #endif
 }
+
+/* minimum/maximum thread stack sizes supported */
+#define THREAD_MIN_STACKSIZE	0x8000		/* 32kB */
+#define THREAD_MAX_STACKSIZE	0x2000000	/* 32MB */
+
+/* set the thread stack size.
+ * Return 0 if size is valid, -1 otherwise.
+ */
+static int
+_pythread_os2_set_stacksize(size_t size)
+{
+	/* set to default */
+	if (size == 0) {
+		_pythread_stacksize = 0;
+		return 0;
+	}
+
+	/* valid range? */
+	if (size >= THREAD_MIN_STACKSIZE && size < THREAD_MAX_STACKSIZE) {
+		_pythread_stacksize = size;
+		return 0;
+	}
+
+	return -1;
+}
+
+#define THREAD_SET_STACKSIZE(x)	_pythread_os2_set_stacksize(x)
diff --git a/Python/thread_pthread.h b/Python/thread_pthread.h
index c29a61c..60d2fb2 100644
--- a/Python/thread_pthread.h
+++ b/Python/thread_pthread.h
@@ -12,6 +12,20 @@
 #endif
 #include <signal.h>
 
+/* The POSIX spec requires that use of pthread_attr_setstacksize
+   be conditional on _POSIX_THREAD_ATTR_STACKSIZE being defined. */
+#ifdef _POSIX_THREAD_ATTR_STACKSIZE
+#ifndef THREAD_STACK_SIZE
+#define	THREAD_STACK_SIZE	0	/* use default stack size */
+#endif
+/* for safety, ensure a viable minimum stacksize */
+#define	THREAD_STACK_MIN	0x8000	/* 32kB */
+#else  /* !_POSIX_THREAD_ATTR_STACKSIZE */
+#ifdef THREAD_STACK_SIZE
+#error "THREAD_STACK_SIZE defined but _POSIX_THREAD_ATTR_STACKSIZE undefined"
+#endif
+#endif
+
 /* The POSIX spec says that implementations supporting the sem_*
    family of functions must indicate this by defining
    _POSIX_SEMAPHORES. */   
@@ -138,15 +152,27 @@
 #if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
 	pthread_attr_t attrs;
 #endif
+#if defined(THREAD_STACK_SIZE)
+	size_t	tss;
+#endif
+
 	dprintf(("PyThread_start_new_thread called\n"));
 	if (!initialized)
 		PyThread_init_thread();
 
 #if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
-	pthread_attr_init(&attrs);
+	if (pthread_attr_init(&attrs) != 0)
+		return -1;
 #endif
-#ifdef THREAD_STACK_SIZE
-	pthread_attr_setstacksize(&attrs, THREAD_STACK_SIZE);
+#if defined(THREAD_STACK_SIZE)
+	tss = (_pythread_stacksize != 0) ? _pythread_stacksize
+					 : THREAD_STACK_SIZE;
+	if (tss != 0) {
+		if (pthread_attr_setstacksize(&attrs, tss) != 0) {
+			pthread_attr_destroy(&attrs);
+			return -1;
+		}
+	}
 #endif
 #if defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
         pthread_attr_setscope(&attrs, PTHREAD_SCOPE_SYSTEM);
@@ -460,3 +486,48 @@
 }
 
 #endif /* USE_SEMAPHORES */
+
+/* set the thread stack size.
+ * Return 0 if size is valid, -1 if size is invalid,
+ * -2 if setting stack size is not supported.
+ */
+static int
+_pythread_pthread_set_stacksize(size_t size)
+{
+#if defined(THREAD_STACK_SIZE)
+	pthread_attr_t attrs;
+	size_t tss_min;
+	int rc = 0;
+#endif
+
+	/* set to default */
+	if (size == 0) {
+		_pythread_stacksize = 0;
+		return 0;
+	}
+
+#if defined(THREAD_STACK_SIZE)
+#if defined(PTHREAD_STACK_MIN)
+	tss_min = PTHREAD_STACK_MIN > THREAD_STACK_MIN ? PTHREAD_STACK_MIN
+						       : THREAD_STACK_MIN;
+#else
+	tss_min = THREAD_STACK_MIN;
+#endif
+	if (size >= tss_min) {
+		/* validate stack size by setting thread attribute */
+		if (pthread_attr_init(&attrs) == 0) {
+			rc = pthread_attr_setstacksize(&attrs, size);
+			pthread_attr_destroy(&attrs);
+			if (rc == 0) {
+				_pythread_stacksize = size;
+				return 0;
+			}
+		}
+	}
+	return -1;
+#else
+	return -2;
+#endif
+}
+
+#define THREAD_SET_STACKSIZE(x)	_pythread_pthread_set_stacksize(x)