The therapeutic protocol is an experimental effort to devise a treatment program for men whose illegal and harmful sexual behavior is unresponsive to conventional psychotherapy alone. Sex offenders may be categorized according to four types. Type one includes offenders who deny the commission of illegal acts or admit the act but deny the illegality. Type two claims that the behavior was caused by either the disinhibiting effect of alcohol or another drug or by temporary insanity. Type three includes the offender whose acts are primarily aggressive and violent and secondarily sexual. Type four, the paraphiliac offender, has a history of fantasies of deviant sexual behavior; diagnosis requires a detailed inquiry into the patient's erotic fantasies. Many forms of psychotherapy have been attempted in treating sex offenders. The verdict regarding the utilities of various types of behavior therapy is not yet in. With regard to hormonal therapy, medroxyprogesterone acetate (MPA) has shown promising results in previous trials. For the experiment conducted at the University of Texas Medical Branch, 10 patients who manifested a type four offender profile received 400 to 500 milligrams per week of MPA intramuscularly for 6 months, followed by gradual reduction of the dose every 3 months thereafter. The hormone proved useful, in conjunction with psychotherapy, in treating this type of offender. The medical risks incurred with this therapy are minimal, but they do require careful monitoring by a physician of the patient's overall physical health. One table, 3 figures, and 86 references are provided.