OBJECTIVE: To determine if women with day 3 serum inhibin-B concentrations < 45 pg/mL (conversion factor to SI unit, 1.00) demonstrate a poorer response to ovulation induction and assisted reproductive technologies outcome relative to women with inhibin-B values > or = 45 pg/mL. DESIGN: Analysis of inhibin-B, FSH, and E2 concentrations in day 3 serum samples. SETTING: Academic clinical practice. PATIENT(S): One hundred fifty-six women who underwent 178 assisted reproductive technology (ART) cycles with luteal phase GnRH agonist suppression plus hMG and urofollitropin stimulation. MAIN OUTCOME MEASURE(S): Serum E2 on day of hCG, number of oocytes retrieved per patient, fertilization rate, cleavage rate, clinical pregnancy rate (PR) per initiated cycle, cancellation rate per initiated cycle, and spontaneous abortion rate. RESULT(S): Women with day 3 serum inhibin-B < 45 pg/mL demonstrated 70% of the E2 response, had 66.6% of the number of oocytes retrieved per patient, with 28% of the clinical PR per initiated cycle, and three times the cancellation rate per initiated cycle than women with day 3 inhibin-B > or = 45 pg/mL. After controlling for age, day 3 serum FSH, day 3 serum E2, patient cycle number, and method of ART, day 3 serum inhibin-B > or = 45 pg/mL was noted to be prognostic of the number of oocytes retrieved and clinical PR. The adjusted odds ratio of clinical pregnancy for those with day 3 serum inhibin-B > or = 45 pg/mL versus those with inhibin-B < 45 pg/mL was 6.8 (95% confidence interval 1.8 to 25.6). CONCLUSION(S): Women with low day 3 serum inhibin-B concentrations demonstrate a poorer response to ovulation induction and are less likely to conceive a clinical pregnancy through ART relative to women with high day 3 inhibin-B.