To examine the possible role of body size and reproductive factors in pancreatic cancer, data were analyzed from a population-based case-control study conducted in Shanghai, China. Cases (n = 451) were permanent residents of Shanghai, 30-74 years of age, newly diagnosed with pancreatic cancer between October 1, 1990, and June 30, 1993. Deceased cases (19%) were excluded from the study. Controls (n = 1,552) were randomly selected from permanent Shanghai residents and frequency-matched to cases by gender and age. Information on body size and reproductive and other possible risk factors was collected through personal interviews. After adjustment for age, income, smoking and other confounders, a positive dose-response relation between body mass index and risk of pancreatic cancer was observed in both sexes. Among women, the risk of pancreatic cancer was significantly associated with number of pregnancies and live births. Compared with 0-2 pregnancies or live births, the odds ratio (OR) for 8 or more pregnancies was 1.90, while that for 5 or more births was 1.88. A modest elevation in risk, independent of parity, was associated with early age at first birth. Risk increased over 40% among women with a first birth at or before age 19 years relative to those at age 26 years or older. Ever use of oral contraceptives was associated with excess risk, though based on small numbers of users. Our findings suggest that, in Shanghai, obesity, gravidity, parity and perhaps use of oral contraceptives are associated with moderate increases in risk of pancreatic cancer, indicating that hormonal determinants deserve further investigation.