To determine whether infertile women have lower antral follicle counts (AFC) than age-matched normal women.Case-control.Academic center.A total of 881 infertile women and 771 women from the community.Antral follicle count and basal hormone measurements.Median AFCs and FSH levels were compared between the two groups within 5-year age strata by using the median test. A subanalysis was performed by identifying women in the control group with a history of attempting conception without success (subfertile group) and with a spontaneous conception in fewer than 12 months resulting in a live birth (fertile group). Age-specific AFC percentiles were calculated and compared within strata determined by age at the time of attempted conception.AFCs were significantly lower in infertile women than in control women across age groups up to 40 years of age. Average FSH levels were significantly higher in the younger-age infertile group versus the community. AFC percentiles differ significantly between fertile and subfertile women within the community up to 40 years of age.Decreased AFC in infertile women suggests that factors affecting the size of the remaining follicle pool in younger women also affect oocyte quality and the likelihood of conception.