diff --git a/Process.h.in b/Process.h.in
index 7f4ea19928d5d1c649c2826da20f66f09842cbca..2017d784b51b02e3523a2e9141dfa705cfa26107 100644
--- a/Process.h.in
+++ b/Process.h.in
@@ -82,7 +82,6 @@
 #  define kwsysProcess_Interrupt kwsys_ns(Process_Interrupt)
 #  define kwsysProcess_Kill kwsys_ns(Process_Kill)
 #  define kwsysProcess_KillPID kwsys_ns(Process_KillPID)
-#  define kwsysProcess_GetParentPID kwsys_ns(Process_GetParentPID)
 #  define kwsysProcess_ResetStartTime kwsys_ns(Process_ResetStartTime)
 #endif
 
@@ -469,13 +468,6 @@ kwsysEXPORT void kwsysProcess_Kill(kwsysProcess* cp);
  */
 kwsysEXPORT void kwsysProcess_KillPID(unsigned long);
 
-#ifndef _WIN32
-/**
- * Get the parent process ID from a given process ID
- */
-kwsysEXPORT unsigned long kwsysProcess_GetParentPID(unsigned long);
-#endif
-
 /**
  * Reset the start time of the child process to the current time.
  */
@@ -546,7 +538,6 @@ kwsysEXPORT void kwsysProcess_ResetStartTime(kwsysProcess* cp);
 #    undef kwsysProcess_Interrupt
 #    undef kwsysProcess_Kill
 #    undef kwsysProcess_KillPID
-#    undef kwsysProcess_GetParentPID
 #    undef kwsysProcess_ResetStartTime
 #  endif
 #endif
diff --git a/ProcessUNIX.c b/ProcessUNIX.c
index 21c57e5973c346328a827eafdf360f6e0103f4b1..ce6bb7b9cf165220cfa682afbe9a8aa81e100a15 100644
--- a/ProcessUNIX.c
+++ b/ProcessUNIX.c
@@ -188,7 +188,6 @@ static void kwsysProcessRestoreDefaultSignalHandlers(void);
 static pid_t kwsysProcessFork(kwsysProcess* cp,
                               kwsysProcessCreateInformation* si);
 static void kwsysProcessKill(pid_t process_id);
-static pid_t kwsysGetParentPID(pid_t process_id);
 #if defined(__VMS)
 static int kwsysProcessSetVMSFeature(char const* name, int value);
 #endif
@@ -2627,73 +2626,6 @@ static void kwsysProcessKill(pid_t process_id)
   kill(process_id, SIGKILL);
 #endif
 }
-unsigned long kwsysProcess_GetParentPID(unsigned long process_id)
-{
-  return kwsysGetParentPID((pid_t)process_id);
-}
-
-static pid_t kwsysGetParentPID(pid_t process_id)
-{
-#if defined(__linux__) || defined(__CYGWIN__)
-  DIR* procdir;
-#endif
-
-#if defined(__linux__) || defined(__CYGWIN__)
-  /* First try using the /proc filesystem.  */
-  if ((procdir = opendir("/proc"))) {
-#  if defined(MAXPATHLEN)
-    char fname[MAXPATHLEN];
-#  elif defined(PATH_MAX)
-    char fname[PATH_MAX];
-#  else
-    char fname[4096];
-#  endif
-    char buffer[KWSYSPE_PIPE_BUFFER_SIZE + 1];
-
-    struct stat finfo;
-    snprintf(fname, sizeof(fname), "/proc/%d/stat", process_id);
-    if (stat(fname, &finfo) == 0) {
-      FILE* f = fopen(fname, "r");
-      if (f) {
-        size_t nread = fread(buffer, 1, 1024, f);
-        fclose(f);
-        buffer[nread] = '\0';
-        if (nread > 0) {
-          char const* rparen = strrchr(buffer, ')');
-          int ppid;
-          if (rparen && (sscanf(rparen + 1, "%*s %d", &ppid) == 1)) {
-            return ppid;
-          }
-        }
-      }
-    }
-    closedir(procdir);
-  } else
-#endif
-  {
-#if defined(KWSYSPE_PS_COMMAND)
-    /* Try running "ps" to get the process information.  */
-    FILE* ps = popen(KWSYSPE_PS_COMMAND, "r");
-
-    /* Make sure the process started and provided a valid header.  */
-    if (ps && fscanf(ps, "%*[^\n]\n") != EOF) {
-      int pid;
-      int ppid;
-      while (fscanf(ps, KWSYSPE_PS_FORMAT, &pid, &ppid) == 2) {
-        if (pid == process_id) {
-          return ppid;
-        }
-      }
-    }
-
-    /* We are done with the ps process.  */
-    if (ps) {
-      pclose(ps);
-    }
-#endif
-  }
-  return 0;
-}
 
 #if defined(__VMS)
 int decc$feature_get_index(char const* name);