Objective: To estimate whether women aged 20-32 years who fulfilled National Institutes of Health criteria for polycystic ovary syndrome (PCOS) would be at higher risk for subsequent development of incident diabetes, dyslipidemia, and hypertension, and to estimate whether normal-weight women with PCOS would have the same degree of cardiovascular risk as overweight women with PCOS. Methods: We estimated the association of PCOS with incident diabetes, dyslipidemia, and hypertension over a period of 18 years among 1,127 white and African-American women in the Coronary Artery Risk Development in Young Adults cohort. We classified women at baseline (ages 20-32 years) based on self-reported symptoms and serum androgen measures using National Institutes of Health PCOS criteria. We estimated the association of PCOS and subsequent cardiovascular risk factors, independent of baseline body mass index (BMI), using multivariable logistic regression. Additionally, among 746 women with a second assessment of PCOS at ages 34-46 years, we estimated the association of persistent PCOS with cardiovascular risk factors. Results: Of 1,127 women, 53 (4.7%) met criteria for PCOS at ages 20-32 years. Polycystic ovary syndrome was associated with a twofold higher odds of incident diabetes (23.1% compared with 13.1%, adjusted odds ratio [AOR] 2.4, confidence interval [CI] 1.2-4.9) and dyslipidemia (41.9% compared with 27.7%, AOR 1.9, CI 1.0-3.6) over the course of 18 years; the association with incident hypertension was not significant (26.9% compared with 26.3%, AOR 1.7, CI 0.8-3.3). Normal-weight women with PCOS (n=31) had a threefold higher odds of incident diabetes compared with normal-weight women without PCOS (AOR 3.1, CI 1.2-8.0). Compared with those without PCOS, women with persistent PCOS (n=11) had the highest odds of diabetes (AOR 7.2, CI 1.1-46.5). Conclusion: Polycystic ovary syndrome is associated with subsequent incident diabetes and dyslipidemia, independent of BMI. Diabetes risk may be greatest for women with persistent PCOS symptoms. © 2010 by The American College of Obstetricians and Gynecologists. Published by Lippincott Williams & Wilkins.