Objective: To evaluate whether the number of ovarian antral follicles, ovarian volume, and ovarian stromal blood flow change with age and to prospectively analyze whether three-dimensional ultrasonographic measurements predict ovarian response and IVF outcome. Design: Prospective analysis. Setting: Assisted reproductive unit. Patient(s): Fifty-six consecutive women 22 to 43 years of age with normal basal serum FSH concentrations who were undergoing their first IVF cycle. Main Outcome Measure(seconds): Number of ovarian antral follicles, ovarian volume, and ovarian stromal flow index were determined by three-dimensional and power Doppler ultrasonography. Pretreatment measurements were compared with number of recovered oocytes, fertilization rates, and pregnancy rates. Result(s): As patient age increased, significant trends in ovarian volume, number of follicles, and stromal vascularity decreased. Three-dimensional ovarian measurements and fertilization rates differed significantly among age groups. For each age group, a higher number of antral follicles, greater ovarian volume, and favorable ovarian stromal vascularity was associated with higher number of retrieved oocytes and increased pregnancy rates. Conclusion(s): Increasing patient age is associated with poor ovarian response, as represented by smaller ovarian volume, lower antral follicle count, and poor stromal vascularity. Three-dimensional power Doppler ultrasonography can help to individualize IVF in patients regardless of age.