Abstract Plasma follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels in samples taken during clomiphene-induced ovulatory cycles in 7 oligo-ovulatory or anovulatory infertile women were determined by radioimmunoassay. These results were compared with results of similar studies made during spontaneous ovulatory cycles in 21 normal volunteers. In the clomiphene-induced ovulatory cycles FSH and LH values were significantly above pretreatment levels after 2 to 3 days of therapy, but subsequently declined prior to a preovulatory peak occurring 13 days after beginning of therapy. Following the preovulatory peak during the luteal phase values declined to the lowest levels observed at any time during the treatment cycle. These changes in plasma FSH and LH concentrations during clomiphene-induced cycles were similar to those seen in normal spontaneous cycles. The early increase in FSH and LH in the induced cycle suggests that the initial site of action of clomiphene is on the hypothalamic-pituitary portion of the hypothalamic-pituitary-ovarian axis. It also suggests that treatment with clomiphene may provide a functional test of this axis.