The role of anthropometric variables in the risk of breast cancer has been investigated using pooled data from 2 hospital-based case-control studies conducted in Italy for a total data-set of 3,247 cases and 3,263 controls. No association was observed in pre-menopausal women between breast cancer risk and height, weight, indices of body mass (W/H2; W/H1.5) and surface area. In post-menopausal women, the risk of breast cancer was inversely related to height, being 0.8 in taller women (greater than 165 cm) compared with women 155 cm tall or less; the trend in risk, although not constantly decreasing, was statistically significant (p trend = 0.03). A direct, statistically significant association emerged with weight and indices of body mass and post-menopausal breast cancer risk. Considering 2 indices of body weight (W/H2 and W/H1.5) and relative to thinner women, the respective estimated risks of post-menopausal breast cancer increased to 1.4 and 1.3 for grossly obese women, and the corresponding p values for trend were respectively 0.002 and 0.02. The role of overweight was more evident in women with early age at menopause, thus suggesting a duration-risk effect.