The objective of this study was to examine the correlates of excessive maternal weight gain among adolescent mothers in the United States. Data from the Centers for Disease Control & Prevention 2000 natality file were analyzed to examine weight gain among adolescents (< or=19 years) compared with their older counterparts (> or=20 years). Using the Institute of Medicine guidelines, we defined excessive weight gain as more than 40 pounds. Our study population was restricted to singleton births, delivered after 36 weeks of gestation, who did not live in California. Maternal weight gain distributions were tabulated by maternal age and other maternal characteristics. Demographic characteristics potentially associated with maternal weight gain were compared for adolescents and older mothers. We further evaluated the role of parity and maternal race on the relationship between excessive weight gain and maternal age. Odds ratios and 95% confidence intervals were estimated using logistic regression. Over 27% of adolescent mothers gained excessive weight during pregnancy, although approximately 18% of their older counterparts gained more than 40 pounds. The association between young maternal age and weight gain was stronger for primiparous women than multiparous women and stronger among non-Hispanic white and non-Hispanic black mothers than Hispanic mothers. Adolescents were more likely to gain excessive weight than their older counterparts in nearly all demographic categories, regardless of parity or race. Adolescents are at high risk of gaining an excessive amount of weight during pregnancy and should be monitored during pregnancy by dietetics professionals.