The tempo, level of growth and maturation during adolescence may have important implications to future adult health. The purpose of the study was to examine factors associated with menarche. Three hundred and forty girls, 9 to 14 years old, were selected from all age eligible girls at Kaiser Permanente Oahu (Honolulu). Girls' age, ethnicity, menstrual status and feeding pattern during infancy were obtained by questionnaire. The mean age of girls was 11.5+/-1.4 yr and the mean age at menarche among 112 (33%) girls who had reached menarche was 11.6+/-1.1 yr. In logistic regression, achievement of menarche was positively explained by age, Asian ethnicity and formula feeding during infancy. In simple linear regression, higher body mass index (BMI) and subcutaneous fat were also positively associated with formula feeding during infancy. The study suggests that girls who were formula fed deposit more body fat than girls who were breast-fed, resulting in early attainment of menarche.