Objectives: In western populations, young age of menarche is associated with increased cardiovascular risk. Little is known about the potential impact of menarche on the metabolic syndrome (as a proxy for cardiovascular risk) in rapidly economically developing populations where age of menarche is falling. We sought to determine the relation between age of menarche and the metabolic syndrome in a rapidly developing Chinese population. Methods: We carried out a retrospective historical cohort study of 7349 women from the Guangzhou Biobank Cohort Study, China, enrolled in 2003-2004. Cardiovascular risk factors were obtained from physical examination; age of menarche was obtained from self-report. The main outcome measure was the metabolic syndrome and its components. Results: Adjusted for age, education, and number of pregnancies, young age of menarche (= 14.5 years was associated with a higher risk of the metabolic syndrome (odds ratio = 1.49; 95% confidence interval = 1.22-1.82), central obesity (1.35; 1.10-1.65), raised blood pressure (1.34; 1.09-1.65), raised fasting glucose (1.40; 1.15-1.71), and higher triglyceride levels (1.36; 1.12-1.67). Further adjustment by waist circumference attenuated these effects, but the odds ratios remained elevated. Conclusions: Earlier age of menarche experienced by younger women in China today, now 12.5 years on average in urban populations, may contribute to an increase in the metabolic syndrome and thereby an increase in cardiovascular disease as these women age. These results further highlight the importance of childhood antecedents of adulthood disease.