A population-based case-control study of 1,233 incident breast cancer cases and 1,241 controls was conducted in Alberta between 1995 and 1997 to examine the influence of anthropometric factors on the risk of breast cancer using several newly derived variables. Data on current height, weight and waist and hip circumference were collected by interviewers using standardized methods. Respondents recalled their body weight at each decade from age 20 to the referent year. Several variables were estimated, and unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs). No statistically significant associations for any of the estimated variables with breast cancer risk for premenopausal women (462 cases, 475 controls) were found. The results for postmenopausal women (771 cases, 762 controls) in the highest vs. lowest quartiles were, for waist circumference, OR = 1.30 (95% CI 0.97–1.73); waist–hip ratio, OR = 1.43 (95% CI 1.07–1.93); weight gain since age 20, OR = 1.35 (05% CI 1.01–1.81); difference between maximum and minimum weights over adult lifetime, OR = 1.56 (95% CI 1.16–2.08); and the reference weight minus the minimum weight since age 20, OR = 1.47 (95% CI 1.10–1.97). Statistically significant trends in risk were observed for these variables. Effect modification with hormone replacement therapy use was found for most variables assessed for postmenopausal women, with much stronger associations found among never-users compared to ever-users. We found strong evidence that waist–hip ratio and weight gained over lifetime, as assessed by different variables, are postmenopausal breast cancer risk factors. These effects were independent of dietary intake and lifetime total physical activity. © 2002 Wiley-Liss, Inc.