To determine the predictive value and to define prognostic threshold measurements for mean ovarian volume (MOV) in patients undergoing IVF. Prospective cohort analysis. Tertiary care center. Two hundred sixtyseven patients. Transvaginal ultrasound before starting gonadotropins. Number of oocytes retrieved, basal hormone levels, and cycle outcomes. The MOV for the population was 4.78 ±2.6 cm3 (range 0.9-21.1 cm3). The MOV significantly correlated with the majority of prestimulation and poststimulation IVF parameters. Threshold analysis demonstrated a lower pregnancy rate associated with a MOV of < 2cm3 (31.6%vs. 55.6%). Threshold analysis revealed a trend toward higher cancellation rate associated with a MOV of < 2cm3 (21.1%vs. 7.3%). Although MOV correlated with IVF stimulation parameters, its use as an adjunct in counseling patients during IVF appears to be of limited value. A MOV < 2 cm3 was associated clinically with a higher cancellation rate (21.1%) and a lower pregnancy rate (31.6%) in those cycles not cancelled. However, these values do not deviate far from the mean national IVF outcome rates. There was no absolute MOV that was predictive of pregnancy outcome or cycle cancellation. To determine the predictive value and to define prognostic threshold measurements for mean ovarian volume (MOV) in patients undergoing IVF. Prospective cohort analysis. Tertiary care center. Two hundred sixtyseven patients. Transvaginal ultrasound before starting gonadotropins. Number of oocytes retrieved, basal The MOV for the population was 4.78 ± 2.6 cm3 (range 0.9-21.1 cm3). The MOV significantly correlated with the majority of prestimulation and poststimulation IVF parameters. Threshold analysis demonstrated a lower pregnancy rate associated with a MOV Threshold analysis revealed a trend toward higher cancellation rate associated with a MOV of <2 cm3 (21.1% vs. 7.3%). While MOV was associated with IVF stimulation parameters, its use as an adjunct in counseling patients during IVF appears to be of limited value. A MOV <2 cm3 was associated clinically with a higher cancellation rate (21.1%) and a lower pregnancy rate (31.6%) in those cycles not canceled. However, these values ​​do not deviate far from the mean national IVF outcome rates. There was no absolute MOV that was predictive of pregnancy outcome or cycle cancellation.