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 E2 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. (Fertil Steril((R)) 2003;79:585-9. (C) 2003 by American Society for Reproductive Medicine.).