diff --git a/lib/libsysdecode/flags.c b/lib/libsysdecode/flags.c
--- a/lib/libsysdecode/flags.c
+++ b/lib/libsysdecode/flags.c
@@ -1195,3 +1195,10 @@
 
 	return (print_mask_0(fp, shmflags, flags, rem));
 }
+
+const char *
+sysdecode_itimer(int which)
+{
+
+	return (lookup_value(itimerwhich, which));
+}
diff --git a/lib/libsysdecode/mktables b/lib/libsysdecode/mktables
--- a/lib/libsysdecode/mktables
+++ b/lib/libsysdecode/mktables
@@ -168,6 +168,7 @@
 	gen_table "sysarchnum" "[A-Z_]+[[:space:]]+[0-9]+"                 "machine/sysarch.h"
 fi
 gen_table "shmflags"  "SHM_[A-Z_]+[[:space:]]+0x[0-9]+"                    "sys/mman.h"         "SHM_ANON"
+gen_table "itimerwhich"     "ITIMER_[A-Z]+[[:space:]]+[0-9]+"              "sys/time.h"
 
 # Generate a .depend file for our output file
 if [ -n "$output_file" ]; then
diff --git a/lib/libsysdecode/sysdecode.h b/lib/libsysdecode/sysdecode.h
--- a/lib/libsysdecode/sysdecode.h
+++ b/lib/libsysdecode/sysdecode.h
@@ -66,6 +66,7 @@
 const char *sysdecode_ipproto(int _protocol);
 void	sysdecode_kevent_fflags(FILE *_fp, short _filter, int _fflags,
 	    int _base);
+const char *sysdecode_itimer(int _which);
 const char *sysdecode_kevent_filter(int _filter);
 bool	sysdecode_kevent_flags(FILE *_fp, int _flags, int *_rem);
 const char *sysdecode_kldsym_cmd(int _cmd);
diff --git a/lib/libsysdecode/sysdecode_enum.3 b/lib/libsysdecode/sysdecode_enum.3
--- a/lib/libsysdecode/sysdecode_enum.3
+++ b/lib/libsysdecode/sysdecode_enum.3
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 14, 2018
+.Dd June 22, 2022
 .Dt sysdecode_enum 3
 .Os
 .Sh NAME
@@ -38,6 +38,7 @@
 .Nm sysdecode_getrusage_who ,
 .Nm sysdecode_idtype ,
 .Nm sysdecode_ipproto ,
+.Nm sysdecode_itimer ,
 .Nm sysdecode_kldsym_cmd ,
 .Nm sysdecode_kldunload_flags ,
 .Nm sysdecode_lio_listio_mode ,
@@ -97,6 +98,8 @@
 .Ft const char *
 .Fn sysdecode_ipproto "int protocol"
 .Ft const char *
+.Fn sysdecode_itimer "int which"
+.Ft const char *
 .Fn sysdecode_kldsym_cmd "int cmd"
 .Ft const char *
 .Fn sysdecode_kldunload_flags "int flags"
@@ -186,6 +189,10 @@
 .Xr procctl 2 ,
 .Xr waitid 2
 .Ta Fa idtype
+.It Fn sysdecode_itimer Ta
+.Xr getitimer 2 ,
+.Xr setitimer 2
+.Ta Fa which
 .It Fn sysdecode_kldsym_cmd Ta Xr kldsym 2 Ta Fa cmd
 .It Fn sysdecode_kldunload_flags Ta Xr kldunloadf 2 Ta Fa flags
 .It Fn sysdecode_lio_listio_mode Ta Xr lio_listio 2 Ta Fa mode