diff --git a/bin/pkill/pkill.c b/bin/pkill/pkill.c
--- a/bin/pkill/pkill.c
+++ b/bin/pkill/pkill.c
@@ -66,8 +66,7 @@
 #define	STATUS_BADUSAGE	2
 #define	STATUS_ERROR	3
 
-#define	MIN_PID	5
-#define	MAX_PID	99999
+#define	PID_MIN	5
 
 /* Ignore system-processes (if '-S' flag is not specified) and myself. */
 #define	PSKIP(kp)	((kp)->ki_pid == mypid ||			\
@@ -868,7 +867,7 @@
 	rval = strtol(line, &endp, 10);
 	if (*endp != '\0' && !isspace((unsigned char)*endp))
 		errx(STATUS_ERROR, "Invalid pid in file `%s'", pidfile);
-	else if (rval < MIN_PID || rval > MAX_PID)
+	else if (rval < PID_MIN || rval > PID_MAX)
 		errx(STATUS_ERROR, "Invalid pid in file `%s'", pidfile);
 	return (rval);
 }
diff --git a/bin/ps/ps.c b/bin/ps/ps.c
--- a/bin/ps/ps.c
+++ b/bin/ps/ps.c
@@ -1469,7 +1469,7 @@
 	intsize = sizeof(pid_max);
 	if (sysctlbyname("kern.pid_max", &pid_max, &intsize, NULL, 0) < 0) {
 		xo_warn("unable to read kern.pid_max");
-		pid_max = 99999;
+		pid_max = PID_MAX;
 	}
 }
 
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -910,6 +910,8 @@
 
 #define	P_MAGIC		0xbeefface
 
+#define	PID_MAX		99999
+
 #ifdef _KERNEL
 
 /* Types and flags for mi_switch(9). */
@@ -954,8 +956,7 @@
  * We use process IDs <= pid_max <= PID_MAX; PID_MAX + 1 must also fit
  * in a pid_t, as it is used to represent "no process group".
  */
-#define	PID_MAX		99999
-#define	NO_PID		100000
+#define	NO_PID		(PID_MAX + 1)
 #define	THREAD0_TID	NO_PID
 extern pid_t pid_max;