OBJECTIVE: To investigate the association between various anthropometric characteristics and breast cancer. DESIGN: Longitudinal prospective cohort study. Follow-up between 1995 and 2000.Subjects:In total, 69 116 women (age: 45-70 years; mean follow-up: 3.6 years), 275 premenopausal and 860 postmenopausal incident invasive breast cancers. MEASUREMENTS: Self-reported height, weight, breast, thorax, waist and hip circumferences and calculated body mass index (BMI) and waist-to-hip ratio (WHR) at baseline. RESULTS: A slight increase in risk with increasing height was found. Weight, BMI, thorax and waist circumferences and WHR were negatively related to breast cancer risk among premenopausal women. The relationships became non significant after additional adjustment for BMI. An increased risk of premenopausal breast cancer with an android body shape (WHR>0.87) might possibly be confined to obese women. Among postmenopausal women, all anthropometric measurements of corpulence were positively associated with breast cancer risk but became non significant after additional adjustment for BMI. No difference in risk of postmenopausal breast cancer according to HRT use was observed. CONCLUSION: The study confirmed that adiposity was negatively associated to premenopausal breast cancer risk and positively associated to postmenopausal breast cancer risk. Further studies will be needed to specify clearly the association between WHR and breast cancer risk, particularly before menopause.