Leuprolide acetate (10(-4) to 10(-5) M) had a stimulatory effect on spontaneous contractions of human myometrium and fallopian tube in vitro. The uterine and tubal tissues were from patients with dysfunctional uterine bleeding that was treated by hysterectomy. Whether the effect of LA on smooth muscle is a component of the mechanism of therapeutic action or an undesirable side effect remains to be determined.