OBJECTIVE: To evaluate effectiveness and safety of a regimen of extended clomiphene citrate (CC) and prednisone for patients who fail treatment with CC alone. DESIGN: Retrospective observational analysis. SETTING: University-based tertiary infertility center. PATIENT(S): Twenty-four anovulatory patients who failed to ovulate after CC 150 mg administered for 5 days. INTERVENTION(S): Treatment consisted of CC given on cycle days 3 through 9 (extended) at a starting dose of 100 to 150 mg/d. Additionally, patients were given prednisone 5 mg orally each night throughout the cycle. MAIN OUTCOME MEASURE(S): Ovulation was confirmed by luteal serum P. Pregnancy was confirmed by rising hCG levels and transvaginal ultrasound. RESULT(S): A total of 60 cycles were available for review. Forty-four of these cycles were ovulatory (73%) and 11 patients (46%) conceived on this therapy. Logistic (two-parameter) pregnancy occurrence over time (cycles) revealed a maximum pregnancy probability of 0.66 and a cycle fecundity of 0.36. No complications of therapy were noted. CONCLUSION(S): Clomiphene citrate-resistant anovulatory patients have high rates of ovulation and pregnancy after treatment with extended CC and prednisone. This therapy offers a potential reduction in cost and risk and should be considered in this group of patients before gonadotropin stimulation or surgery.