A deficiency in follicle stimulating hormone (FSH) levels during the early follicular phase of the menstrual cycle has been shown to result in luteal phase defect (LPD). A short course of human urinary FSH (uFSH) (Metrodin, Serono Laboratories) was given for a maximum of six cycles to 18 women with endometrial-biopsy-proven (EBX-proven) LPD. Adjunctive therapy in the form of midcycle human chorionic gonadotropin was given after the third therapy cycle. The uFSH therapy reduced the mean EBX lag time (2.0 +/- 0.6 days with therapy vs. 4.1 +/- 0.4 pretherapy, P less than .01), normalized the follicular phase length (15 +/- 0.4 days vs. 17.2 +/- 0.8 pretherapy, P less than .25) and increased the luteal phase length (12.7 +/- 0.4 days vs. 10.8 +/- 0.2 pretherapy, P less than .001). Twelve of 46 cycles (26%) in which uFSH was given without adjunctive therapy were anovulatory. Seven patients conceived; the result was seven viable pregnancies, all delivered at term. The cumulative pregnancy rate approached 48% by the sixth therapy cycle. uFSH therapy is useful for the correction of LPD and yields an acceptable pregnancy rate.