During the five years ending on December 31, 1981, 159 anovulatory and oligomenorrheic patients were treated with clomiphene citrate for induction of ovulation. Overall, 86% of these patients ovulated, and 49% of the patients who ovulated conceived. Life table analysis was employed to investigate factors contributing to reduced conception rates, including abnormal semen analysis, pelvic or tubal abnormalities, and poor cervical mucus. Elevated serum testosterone levels did not affect conception rates. The most significant factor contributing to reduced overall pregnancy rates was patient discontinuation of therapy. Cumulative pregnancy rates corrected for discontinuation approach 100% after ten cycles of therapy. During this period, the monthly probability of pregnancy (monthly fecundability) remained constant. Optimal pregnancy rates are attained if other infertility factors are corrected and treatment is continued for ten to 12 ovulatory cycles.