Purpose: The purpose of this study is to determine if baseline antral follicle assessment may serve as additional information in predicting in vitro fertilization outcome. Methods: Prospective, descriptive preliminary study of in vitro fertilization outcome. From July 1998 to July 1999 224 patients underwent antral follicle assessment (follicle 2-6 mm in diameter) on baseline of the planned, stimulated in vitro fertilization cycle. The outcomes were analyzed with respect to antral follicle assessment (less than or equal to6 or >6), basal cycle day 3 follicle stimulated harmone (less than or equal to 10 or > 10 IU/L) and maternal age (less than or equal to 35 or > 35 years). Results: The clinical pregnancy rate was significantly higher in the group with baseline antral follicle >6 compared to that in the group with antral follicle less than or equal to6 (51% vs. 19%, respectively). Controlling for patient age, and basal follicle stimulated harmone, the pregnancy rate was significantly higher in the group with antral follicle >6 compared to that in the group with antral follicle less than or equal to6. The cancellation rate was significantly increased with advancing maternal age, elevated basal follicle stimulated harmone levels, and baseline antral follicle less than or equal to6. The cancellation rate was significantly higher in the group with antral follicle >6 compared to that in the group with antral follicle greater than or equal to6 (33% vs. 1%, respectively). Conclusions: In vitro fertilization outcome is strongly correlated with both maternal ages, basal cycle, day 3 follicle, stimulated harmone, and antral follicle assessment. Antral follicle assessment was a better predictor of in vitro fertilization outcome than were age or follicle stimulated harmone. Antral follicle assessment may provide a marker for ovarian age that is distinct from chronological age or hormonal markers.