Standards of penile and clitoral sizes are useful for diagnosis of genital abnormalities. In order to verify whether ethnicity has an effect on the size of external genitalia in newborns, 570 full term infants, Jews (221) and Bedouins (349), at the neonatal department of the Soroka Medical Center were examined. Clitoral length, the distance between the center of the anus to the fourchette (AF) and the distance between the center of the anus and the base of the clitoris (AC) were measured, and the AF/AC ratio was calculated for the females. Penile length was measured in the males. Significant differences in clitoral length (12.6%) between the Jewish group (5.87 +/- 1.48 mm) and the Bedouin group (6.61 +/- 1.72 mm) (p < 0.01) and in the ratio of AF to AC between the two ethnic groups (p < 0.01) were found. To the best of our knowledge, our study is the first to report ethnic differences in genital sizes of newborns.