The recent increase in requests for genital examinations in girls who may have been sexually abused has necessitated detailed information not previously available on normal anatomy of the prepubertal girl. This study was undertaken to document the genital anatomy of 211 girls between the ages of 1 month and 7 years who presented for well child care or nongynecologic complaints and who had no history of sexual abuse. Each child's genitalia was examined and photographed, with findings reported reflecting those observed photographically. The study population consisted of 36% blacks, 33.6% white non-Hispanics, 29.9% Hispanics, and 0.5% Asians. Subjects had a mean age of 21 +/- 20.6 (SD) months. Extensive labial agglutination sufficient to obscure the hymen was noted in 5% (10/211) and partial agglutination in an additional 17% (35/211). A significant difference was noted in hymenal configuration by age, with a fimbriated hymen the most common type (46%) in infants aged 12 months or younger and a crescentic hymen the most common (51%) in girls older than 24 months (P less than or equal to .001). No significant difference was noted in hymen configuration by race. Hymenal bumps (mounds) were observed in 7%, hymenal tags in 3%, vestibular bands in 98%, longitudinal intravaginal ridges in 25%, and external ridges in 15% of subjects in whom the anatomy under study could be visualized. Hymenal notches (clefts) occurred superiorly and laterally on the hymenal rim but none were found inferiorly on the lower half of the hymen. A narrow rounded hymenal ring with a transection was observed in only 1 (0.5%) of 201 subjects and was not considered a normal finding.(ABSTRACT TRUNCATED AT 250 WORDS)