OBJECTIVE: To investigate whether the prevention of early follicular growth by luteal E(2) administration improves the relationship between day 3 hormone measurements and the ovarian follicular status. DESIGN: Prospective, cohort study. SETTING: Assisted reproductive technology unit in Clamart, France. PATIENT(S): One hundred sixty-two infertile women. INTERVENTION(S): Participants received oral 17beta-E(2), 4 mg/day, from day 20 to the next cycle day 1 (n = 81) or served as controls (n = 81). Serum E(2), inhibin B, and FSH were measured during the 3 days after E(2) discontinuation (FD1, FD2, and FD3) in E(2)-treated women and on cycle day 3 (CD3) in controls. Early antral follicles were counted at ultrasound scans on FD3 and CD3. MAIN OUTCOME MEASURE(S): Hormonal-follicular correlations on FD3 and CD3. RESULT(S): As expected, after E(2) withdrawal, inhibin B and FSH increased from FD1 to FD3 whereas E(2) decreased. Correlations between FSH and inhibin B and follicular counts were stronger on FD3 than on CD3. CONCLUSION(S): Luteal E(2) administration notably strengthens the relationship between serum FSH and inhibin B levels and the number of antral follicles on day 3. This approach may represent an alternative test of ovarian follicular status.