diff -uNr tcl8.0.5.ORIG/generic/tclEnv.c tcl8.0.5/generic/tclEnv.c
--- tcl8.0.5.ORIG/generic/tclEnv.c	Wed Feb  3 08:01:59 1999
+++ tcl8.0.5/generic/tclEnv.c	Thu Oct 11 13:39:25 2001
@@ -15,6 +15,7 @@
  * RCS: @(#) $Id: tclEnv.c,v 1.3 1999/02/02 23:01:59 stanton Exp $
  */
 
+#define __IN_TCLENV__
 #include "tclInt.h"
 #include "tclPort.h"
 
@@ -101,6 +102,9 @@
     if (environ == NULL) {
 	environSize = TclMacCreateEnv();
     }
+#endif
+#ifdef __APPLE__
+    environ = *_NSGetEnviron();
 #endif
 
     /*
diff -uNr tcl8.0.5.ORIG/unix/tclUnixPort.h tcl8.0.5/unix/tclUnixPort.h
--- tcl8.0.5.ORIG/unix/tclUnixPort.h	Wed Sep 30 03:22:39 1998
+++ tcl8.0.5/unix/tclUnixPort.h	Thu Oct 11 14:06:13 2001
@@ -99,6 +99,16 @@
 #include <netdb.h>		/* gethostbyname() */
 
 /*
+ * On MacOS X, extern char** environ is in crt1.o which * cannot be linked 
+ * into any dynamiclib as requested by -twolevel_namespace.
+ * One should use NSGetEnviron() to set it.
+ */
+
+#ifdef __APPLE__
+#include <crt_externs.h>
+#endif
+
+/*
  * Some platforms (e.g. SunOS) don't define FLT_MAX and FLT_MIN, so we
  * look for an alternative definition.  If no other alternative is available
  * we use a reasonable guess.
@@ -452,10 +462,14 @@
  * Variables provided by the C library:
  */
 
-#if defined(_sgi) || defined(__sgi)
+#if defined(_sgi) || defined(__sgi) || defined(__APPLE__)
 #define environ _environ
 #endif
+#if defined(__IN_TCLENV__) && defined(__APPLE__)
+char **environ;
+#else
 extern char **environ;
+#endif
 
 /*
  * At present (12/91) not all stdlib.h implementations declare strtod.