This review of the status of the biological control of stable flies suggests that little is known about pathogens of these flies and that this area of study is largely unexplored. Predators are acknowledged to have a great effect on stable fly populations, but they generally fail to provide satisfactory control. Predators are usually very difficult to augment to increase their effectiveness. Parasitic wasps, at present, offer the greatest potential for biological control of stable flies. They attack the pupal stage of the host, which generally is not subject to attack by predators and pathogens; and they can be easily and inexpensively mass produced. Attempts to control stable flies on midwestern livestock confinements have not been successful, but recent studies have added greatly to our knowledge of this group of biological control agents. This new knowledge should increase their effectiveness.