PIP: A combination of 100 mcg of (EE) ethinyl estradiol combined with 1.0 mg of dl-norgestrel has been employed in this study as a postcoital contraceptive. A total of 143 women, 18-42 years old, were treated for a total of 148 treatment cycles. Treatment was instituted as soon as possible after exposure and no later than 5 days after exposure. No side effects were encountered. There were 3 pregnancies in this study group, all among patients who were regularly cycling. There is some question in all 3 cases as to whether these pregnancies were truly a result of method failure. Histologic examination of endometrial biopsies taken on the 1st day of bleeding following treatment are highly suggestive that the endometrial stroma undergoes more rapid maturation than do the glands. This "out of phase" pattern suggest that there is a significant effect of the medication on the endometrium.