Purpose: Correlation between prenatal and postnatal penile and clitoral sizes has not been reported.These data would substantiate the ability of prenatal ultrasound (US) scan to predict postnatal measurements.The aims were to correlate prenatal and postnatal penile and clitoral measurements and to ascertain the possible advantage of using prenatal penile width rather than length to predict postnatal measurements.Methods: This was a longitudinal study.Fetal penis and clitoris were measured by high-resolution US between gestational weeks 14-29.Postnatal measurements of external genitalia were performed during the first postnatal week.All measurements were performed twice.A correlation between the measurements sets was sought.Results: Paired prenatal and postnatal measurements were performed on 46 males and 48 females.Prenatal penile and clitoral length values correlated significantly to postnatal length atp <.05, each.Conclusions: This is the first study to compare prenatal and postnatal penile and clitoral measurements.Prenatal US findings appear to be reliable indicators of postnatal penile and clitoral length measurements.Penile width measurement did not add new information.