diff --git a/aom_ports/aom_once.h b/aom_ports/aom_once.h
index 37057e6..354ed9d 100644
--- a/aom_ports/aom_once.h
+++ b/aom_ports/aom_once.h
@@ -58,29 +58,6 @@
   InitOnceComplete(&aom_init_once, 0, NULL);
 }
 
-#elif CONFIG_MULTITHREAD && defined(__OS2__)
-#define INCL_DOS
-#include <os2.h>
-static void aom_once(void (*func)(void)) {
-  static volatile int done;
-
-  /* If the initialization is complete, return early. */
-  if (done) return;
-
-  /* Causes all other threads in the process to block themselves
-   * and give up their time slice.
-   */
-  DosEnterCritSec();
-
-  if (!done) {
-    func();
-    done = 1;
-  }
-
-  /* Restores normal thread dispatching for the current process. */
-  DosExitCritSec();
-}
-
 #elif CONFIG_MULTITHREAD && HAVE_PTHREAD_H
 #include <pthread.h>
 static void aom_once(void (*func)(void)) {
diff --git a/aom_util/aom_thread.h b/aom_util/aom_thread.h
index 8d04312..8fdcd9e 100644
--- a/aom_util/aom_thread.h
+++ b/aom_util/aom_thread.h
@@ -138,151 +138,6 @@
   ok = SleepConditionVariableCS(condition, mutex, INFINITE);
   return !ok;
 }
-#elif defined(__OS2__)
-#define INCL_DOS
-#include <os2.h>  // NOLINT
-
-#include <errno.h>        // NOLINT
-#include <stdlib.h>       // NOLINT
-#include <sys/builtin.h>  // NOLINT
-
-#define pthread_t TID
-#define pthread_mutex_t HMTX
-
-typedef struct {
-  HEV event_sem_;
-  HEV ack_sem_;
-  volatile unsigned wait_count_;
-} pthread_cond_t;
-
-//------------------------------------------------------------------------------
-// simplistic pthread emulation layer
-
-#define THREADFN void *
-#define THREAD_RETURN(val) (val)
-
-typedef struct {
-  void *(*start_)(void *);
-  void *arg_;
-} thread_arg;
-
-static void thread_start(void *arg) {
-  thread_arg targ = *(thread_arg *)arg;
-  free(arg);
-
-  targ.start_(targ.arg_);
-}
-
-static INLINE int pthread_create(pthread_t *const thread, const void *attr,
-                                 void *(*start)(void *), void *arg) {
-  int tid;
-  thread_arg *targ = (thread_arg *)malloc(sizeof(*targ));
-  if (targ == NULL) return 1;
-
-  (void)attr;
-
-  targ->start_ = start;
-  targ->arg_ = arg;
-  tid = (pthread_t)_beginthread(thread_start, NULL, 1024 * 1024, targ);
-  if (tid == -1) {
-    free(targ);
-    return 1;
-  }
-
-  *thread = tid;
-  return 0;
-}
-
-static INLINE int pthread_join(pthread_t thread, void **value_ptr) {
-  (void)value_ptr;
-  return DosWaitThread(&thread, DCWW_WAIT) != 0;
-}
-
-// Mutex
-static INLINE int pthread_mutex_init(pthread_mutex_t *const mutex,
-                                     void *mutexattr) {
-  (void)mutexattr;
-  return DosCreateMutexSem(NULL, mutex, 0, FALSE) != 0;
-}
-
-static INLINE int pthread_mutex_trylock(pthread_mutex_t *const mutex) {
-  return DosRequestMutexSem(*mutex, SEM_IMMEDIATE_RETURN) == 0 ? 0 : EBUSY;
-}
-
-static INLINE int pthread_mutex_lock(pthread_mutex_t *const mutex) {
-  return DosRequestMutexSem(*mutex, SEM_INDEFINITE_WAIT) != 0;
-}
-
-static INLINE int pthread_mutex_unlock(pthread_mutex_t *const mutex) {
-  return DosReleaseMutexSem(*mutex) != 0;
-}
-
-static INLINE int pthread_mutex_destroy(pthread_mutex_t *const mutex) {
-  return DosCloseMutexSem(*mutex) != 0;
-}
-
-// Condition
-static INLINE int pthread_cond_destroy(pthread_cond_t *const condition) {
-  int ok = 1;
-  ok &= DosCloseEventSem(condition->event_sem_) == 0;
-  ok &= DosCloseEventSem(condition->ack_sem_) == 0;
-  return !ok;
-}
-
-static INLINE int pthread_cond_init(pthread_cond_t *const condition,
-                                    void *cond_attr) {
-  int ok = 1;
-  (void)cond_attr;
-
-  ok &=
-      DosCreateEventSem(NULL, &condition->event_sem_, DCE_POSTONE, FALSE) == 0;
-  ok &= DosCreateEventSem(NULL, &condition->ack_sem_, DCE_POSTONE, FALSE) == 0;
-  if (!ok) {
-    pthread_cond_destroy(condition);
-    return 1;
-  }
-  condition->wait_count_ = 0;
-  return 0;
-}
-
-static INLINE int pthread_cond_signal(pthread_cond_t *const condition) {
-  int ok = 1;
-
-  if (!__atomic_cmpxchg32(&condition->wait_count_, 0, 0)) {
-    ok &= DosPostEventSem(condition->event_sem_) == 0;
-    ok &= DosWaitEventSem(condition->ack_sem_, SEM_INDEFINITE_WAIT) == 0;
-  }
-
-  return !ok;
-}
-
-static INLINE int pthread_cond_broadcast(pthread_cond_t *const condition) {
-  int ok = 1;
-
-  while (!__atomic_cmpxchg32(&condition->wait_count_, 0, 0))
-    ok &= pthread_cond_signal(condition) == 0;
-
-  return !ok;
-}
-
-static INLINE int pthread_cond_wait(pthread_cond_t *const condition,
-                                    pthread_mutex_t *const mutex) {
-  int ok = 1;
-
-  __atomic_increment(&condition->wait_count_);
-
-  ok &= pthread_mutex_unlock(mutex) == 0;
-
-  ok &= DosWaitEventSem(condition->event_sem_, SEM_INDEFINITE_WAIT) == 0;
-
-  __atomic_decrement(&condition->wait_count_);
-
-  ok &= DosPostEventSem(condition->ack_sem_) == 0;
-
-  pthread_mutex_lock(mutex);
-
-  return !ok;
-}
 #else                 // _WIN32
 #include <pthread.h>  // NOLINT
 #define THREADFN void *
diff --git a/common/tools_common.c b/common/tools_common.c
index 6b579e0..2d366e2 100644
--- a/common/tools_common.c
+++ b/common/tools_common.c
@@ -26,15 +26,9 @@
 #include "aom/aomdx.h"
 #endif
 
-#if defined(_WIN32) || defined(__OS2__)
+#if defined(_WIN32)
 #include <io.h>
 #include <fcntl.h>
-
-#ifdef __OS2__
-#define _setmode setmode
-#define _fileno fileno
-#define _O_BINARY O_BINARY
-#endif
 #endif
 
 #define LOG_ERROR(label)               \
@@ -50,7 +44,7 @@
 
 FILE *set_binary_mode(FILE *stream) {
   (void)stream;
-#if defined(_WIN32) || defined(__OS2__)
+#if defined(_WIN32)
   _setmode(_fileno(stream), _O_BINARY);
 #endif
   return stream;