The investigational use of prostaglandins to establish a safe, alternative method for the termination of pregnancy has shown significant development in the United States. The introduction of second generation compounds was initiated by chemically attaching a methyl group in the 15 carbon position of prostaglandins E2 and F2alpha. These compounds prevented enzymatic degradation by the enzyme prostaglandin 15 dehydrogenase. (15S)-15 methyl prostaglandin E2 methyl ester administered by intramuscular injection has been used successfully to therapeutically terminate pregnancy in 208 women of gestational age six through 20 weeks. Side effects, not major and considered acceptable by the investigator, were vomiting, diarrhea and temperature elevations associated with shaking and chills. (15S)-15 methyl prostaglandin F2alpha (THAM), administered by intramuscular injection, has been used to terminate pregnancy in 283 women. Efficacy rates under optimal dosage regimens have reached 100% with a complete abortion rate of 96%. Gastrointestinal side effects of vomiting and diarrhea occurred, but temperature elevations with associated shaking and chills were infrequent. The mean time from initial therapy to abortion with both compounds has remained under 16 hours. A route of drug therapy for therapeutic termination of human pregnancy has been explored and developed which avoids invasion of the uterus.