• The clinical usefulness of gynecologic age (GA) (the difference between chronologic age [CA] and menarchal age [MA]) is controversial. We compared CA and GA with bone age (BA) (the standard reference criterion for biologic maturity), in 107 Caucasian girls who ranged in age from 8.3 to 18.5 years. Chronologic age and GA each correlated significantly with BA. Regression analysis revealed no significant difference between the BAs of early-maturing girls and late-maturing girls of the same CA. However, the BAs of late-maturing girls were significantly greater than those of early-maturing girls of the same GA. Chronologic age may be preferable to GA in studies of adolescents that require an assessment of biologic maturity because CA is a more accurate measure of BA than is GA.