Birth weights of 422 infants born to primigravid patients under the age of 16 years were compared with the birth weights of 422 infants born to a racially comparable group of primigravid patients 20 to 24 years old. No significant difference in birth weights was found between the two groups. Although infants of adolescents were born of shorter gestations than infants of older women, overall mean birth weights were similar, since the infants of adolescents were heavier at gestations of less than 37 weeks. Race and sex of the infant were more important predictors of birth weight among the adult group, whereas the maternal gain in weight was a more important factor among the adolescent group. Reduced birth weights reported in previous studies among infants of adolescents may have been due to overrepresentation of risk factors among these mothers rather than to maternal age, per se.