An abnormally small preputial orifice, resulting in inability to extrude the penis, can be congenital, or acquired as a result of neoplasia, edema, or fibrosis after trauma, inflammation, or infection. Clinical signs are variable. Usually, the problem is unnoticed until the dog attempts to mate and is unable to copulate. Urine can pool in the prepuce and cause posthitis. Diagnosis is established by physical examination of the prepuce and penis. Treatment depends on severity of the stenosis and intended use of the dog. If the dog is not used for breeding, therapy probably is not needed, although castration should be considered to prevent arousal. Surgical enlargement of the preputial orifice is indicated if the animal is to be used for breeding, if the phimosis contributes to balanoposthitis, or in the unlikely event that phimosis interferes with normal micturition.