diff --git a/bin/ikarus b/bin/ikarus
index 1e73a8c..653d817 100755
Binary files a/bin/ikarus and b/bin/ikarus differ
diff --git a/bin/ikarus-runtime.c b/bin/ikarus-runtime.c
index 515895d..26d036d 100644
--- a/bin/ikarus-runtime.c
+++ b/bin/ikarus-runtime.c
@@ -905,3 +905,16 @@ ikrt_bytes_allocated_major(ikpcb* pcb){
   return fix(pcb->allocation_count_major);
 }
 
+
+ikp 
+ikrt_fork(){
+  int pid = fork();
+  return fix(pid);
+}
+
+ikp 
+ikrt_waitpid(ikp pid){
+  int status;
+  pid_t t = waitpid(unfix(pid), &status, 0);
+  return fix(t);
+}
diff --git a/src/ikarus.boot b/src/ikarus.boot
index cd03ec9..3c8e413 100644
Binary files a/src/ikarus.boot and b/src/ikarus.boot differ
diff --git a/src/libposix.ss b/src/libposix.ss
index 6e80eef..57c7146 100644
--- a/src/libposix.ss
+++ b/src/libposix.ss
@@ -1,16 +1,22 @@
 
-;;; ($pcb-set! posix-fork
-;;;   (lambda ()
-;;;     (foreign-call "S_fork")))
-;;; 
-;;; ($pcb-set! fork
-;;;   (lambda (parent-proc child-proc)
-;;;     (let ([pid (posix-fork)])
-;;;       (cond
-;;;         [(fx= pid 0) (child-proc)]
-;;;         [(fx= pid -1) 
-;;;          (error 'fork "failed")]
-;;;         [else (parent-proc pid)]))))
+(primitive-set! 'posix-fork
+  (lambda ()
+    (foreign-call "ikrt_fork")))
+
+(primitive-set! 'fork
+  (lambda (parent-proc child-proc)
+    (let ([pid (posix-fork)])
+      (cond
+        [(fx= pid 0) (child-proc)]
+        [(fx= pid -1) 
+         (error 'fork "failed")]
+        [else (parent-proc pid)]))))
+
+(primitive-set! 'waitpid
+  (lambda (pid)
+    (unless (fixnum? pid)
+      (error 'waitpid "~s is not a fixnum" pid))
+    (foreign-call "ikrt_waitpid" pid)))
 
 (primitive-set! 'system
   (lambda (x)
diff --git a/src/makefile.ss b/src/makefile.ss
index 4fef4cc..68b0279 100755
--- a/src/makefile.ss
+++ b/src/makefile.ss
@@ -86,6 +86,7 @@
     make-guardian weak-cons collect 
     interrupt-handler
     time-it 
+    posix-fork fork waitpid
     ))
 
 (define system-primitives