Disadvantaged pregnant black teenagers have a higher proportion of low-birth-weight infants and their offspring have a lower mean birth weight. One hundred and fifty-seven pregnant adolescents enrolled in a Baltimore public school for pregnant teenagers were studied to determine the impact of a nutritional supplement on pregnancy outcome. Seventy-eight students voluntarily agreed to receive a nutritional supplement; 79 comparably matched students did not receive the supplement. The supplement Sustacal provided a mean intake of 8691 cal with 530 g of protein and additional vitamins and minerals over an average period of 15.1 weeks. This supplement was associated with a significant increase of 157 g in the mean infant birth weight (P less than 0.05). A significant increase in infant birth weight of 269 g was noted in the offspring of supplemented girls below 16 years of age compared with the nonsupplemented girls below this age (P less than 0.05). Significant differences in infant birth weight were also noted in the offspring of nonsmoking supplemented adolescents (P less than 0.05). The proportion of low-birth-weight infants was decreased in the supplemented subjects, but the difference was not significant.