The activity of the corpus luteum, the endometrium and the trophoblast was studied after local medical treatment of 31 women with tubal pregnancy. We measured the serum concentration of progesterone, the secretory endometrial protein placental protein 14 (PP14), and human chorionic gonadotrophin (HCG) before and after treatment by injection of prostaglandin F2 alpha into the site of the gestation and into the corpus luteum. There was no significant difference in the pre-treatment serum progesterone and serum PP14 concentrations of 26 women who were treated successfully and of five women, who were operated on after failure of the treatment. After the prostaglandin treatment the serum progesterone and PP14 concentrations decreased simultaneously with the serum HCG concentration or remained at a low, constant concentration. We conclude that measurement of serum progesterone and PP14 cannot be used for selection of patients for treatment by prostaglandin F2 alpha or for monitoring the effect of the treatment. The injection of prostaglandin into the ovary has either no effect on the activity of the corpus luteum or induces only a partial luteolysis.