Background: Previous studies have shown that early menarche is associated with elevated adiposity in adulthood. This relationship was not well-examined in Hong Kong Chinese women. The purposes of this study were: 1) to examine the associations between age at menarche and adult body mass index (BMI) and adiposity; 2) to determine whether weight change from age 18 to middle age modifies the relationship between early menarche and adult adiposity. Methods: A life-course epidemiology study named “Hong Kong Women’s Health Study” was conducted among Chinese female nurses in Hong Kong. Three rounds of mail surveys were implemented and 1253 nurses aged 35 to 65 years were involved in this study. Age at menarche, height, weight at age 18, current weight, waist circumference and other variables were collected by a self-administered questionnaire. Weight change was calculated as current weight minus weight at age 18. The self-reported anthropometric variables have been validated in a pilot study. Results: The mean age at menarche was 12.5±1.4 years. Nearly one fourth (23.9%) of the women had early menarche (≤11 years). The mean weight change was 5.8±6.8 kg. Women with early menarche had higher body weight at age 18 (51.6 kg vs. 48.6 kg, p<0.001) but lesser weight change from age 18 to current (5.0 kg vs. 6.0 kg, p<0.05) than those without early menarche. Using regression analyses, after adjustment for age, height, and physical activity, one year increase in age at menarche was associated with 0.21 kg/m2 decrease in BMI (95% CI: -0.33 to -0.09, p<0.001); early menarche was significantly associated with overweight/obesity (OR=1.64, 95% CI: 1.23 to 2.19, p<0.01) and central adiposity (OR=1.73, 95% CI: 1.29 to 2.32, p<0.001). All these associations were strengthened after further adjustment of weight change (all p<0.01). In the stratified analysis, the ORs were 1.49 and 1.68 for overweight/obesity and central adiposity in weight gain group (gained weight > 1 kg), and 2.85 and 1.69 in weight loss group (lost weight > 1 kg), respectively (all p<0.05). Conclusions: Our study indicated that early menarche predicted greater BMI and elevated adiposity in adulthood. This association could not be eliminated by weight change status, even if the women had reduced body weight from young adulthood to middle age.