A cohort of 213 girls (aged 10 y, range +/- 9 mo) whose parents reported their dietary intakes (including nutritional supplements) using a semiquantitative food frequency questionnaire, was followed for 4 y until 82% of the 194 parents who responded to follow-up letters had reported that their daughters had had their first menstrual periods. The relative risk (RR) of menarche before age 12.5 y was 2.0 [95% confidence interval (CI) = 1.1-3.8] for the tallest girls (greater than 150 cm) compared with the shortest girls (less than 130 cm). The RR was 2.1 (95% CI = 1.1-3.8) for the fattest girls [Quetelet's index of relative weight (in kg/m2) greater than 19] vs the leanest girls (less than 15). After adjusting for height and Quetelet's index, menarcheal age was not associated with intake of energy nor energy-adjusted intake of protein, fat, or carbohydrate. The overall results are consistent with the hypothesis that nutritional factors influence age at menarche mainly through their effects on accumulation of adipose tissue.