diff --git a/configure.ac b/configure.ac
index 494db94..24b4d90 100644
--- a/configure.ac
+++ b/configure.ac
@@ -40,8 +40,9 @@ AC_INIT(README)
 AC_ENABLESUBDIR
 AC_SRCDIR_PREFIX(srcdir_prefix)
 AC_HEADLINE(dnl
-GNU Pth, Portable Threads, dnl
+pthsem, Portable Threads, dnl
 PTH_VERSION, pth_vers.c, dnl
+[Copyright (c) 2005-2006 Martin Koegler <mkoegler@auto.tuwien.ac.at>] 
 [Copyright (c) 1999-2006 Ralf S. Engelschall <rse@engelschall.com>])
 AC_CONFIG_PARAM(config.param)
 AC_CONFIG_HEADER(pth_acdef.h)dnl
@@ -640,6 +641,17 @@ AC_CHECK_EXTLIB(Dmalloc, dmalloc, dmallo
                 AC_DEFINE(PTH_DMALLOC, 1, [define if using Dmalloc in GNU pth]))
 
 dnl ##
+dnl ##  Valgrind support
+dnl ##
+
+AC_ARG_WITH(valgrind,[  --with-valgrind[[=DIR]]   include annotation for valgrind (default=no)],[
+  if test -d "$with_valgrind"; then
+	CPPFLAGS="$CPPFLAGS -I$with_valgrind/include"
+  fi
+  AC_CHECK_DEFINE(VALGRIND_STACK_REGISTER, valgrind/valgrind.h) 
+])
+
+dnl ##
 dnl ##  OUTPUT SUBSTITUTION
 dnl ##
 
diff --git a/pth_tcb.c b/pth_tcb.c
index bb8ec84..10ba2c6 100644
--- a/pth_tcb.c
+++ b/pth_tcb.c
@@ -84,10 +84,17 @@ #ifdef PTH_EX
     /* per-thread exception handling */
     ex_ctx_t       ex_ctx;               /* exception handling context                  */
 #endif
+#ifdef HAVE_VALGRIND_STACK_REGISTER
+    int           stack_id;              /* stack id for valgrind                        */ 
+#endif
 };
 
 #endif /* cpp */
 
+#ifdef HAVE_VALGRIND_STACK_REGISTER
+#include <valgrind/valgrind.h>
+#endif
+
 intern const char *pth_state_names[] = {
     "scheduler", "new", "ready", "running", "waiting", "dead"
 };
@@ -108,6 +115,7 @@ intern pth_t pth_tcb_alloc(unsigned int 
         stacksize = SIGSTKSZ;
     if ((t = (pth_t)malloc(sizeof(struct pth_st))) == NULL)
         return NULL;
+    memset (t, 0, sizeof(struct pth_st));
     t->stacksize  = stacksize;
     t->stack      = NULL;
     t->stackguard = NULL;
@@ -120,6 +128,9 @@ intern pth_t pth_tcb_alloc(unsigned int 
                 pth_shield { free(t); }
                 return NULL;
             }
+#ifdef HAVE_VALGRIND_STACK_REGISTER
+        t->stack_id = VALGRIND_STACK_REGISTER (t->stack, t->stack + stacksize);
+#endif
         }
 #if PTH_STACKGROWTH < 0
         /* guard is at lowest address (alignment is guarrantied) */
@@ -138,8 +149,12 @@ intern void pth_tcb_free(pth_t t)
 {
     if (t == NULL)
         return;
-    if (t->stack != NULL && !t->stackloan)
+    if (t->stack != NULL && !t->stackloan) {
+#ifdef HAVE_VALGRIND_STACK_REGISTER
+        VALGRIND_STACK_DEREGISTER (t->stack_id);
+#endif
         free(t->stack);
+    }
     if (t->data_value != NULL)
         free(t->data_value);
     if (t->cleanups != NULL)