Mortality from cancer of the prostate is increasing in the Asia-Pacific, when much of this region is undergoing a transition to a Western lifestyle. The role that lifestyle factors play in prostate cancer appears limited, but existing data mainly are from the West. We conducted an individual participant data analysis of 24 cohort studies involving 320,852 men (83% in Asia). Cox proportional hazard models were used to quantify associations between risk factors and mortality from prostate cancer. There were 308 deaths from prostate cancer (14% in Asia) during 2.1 million person-years of follow-up. The age-adjusted hazard ratio (95% confidence interval; CI) for men with body mass index (BMI) 28 kg/m2 or more, compared with below 25, was 1.55 (1.12 - 2.16); no such significant relationship was found for height or waist circumference. The BMI result was unchanged after adjustment for other variables, was consistent between Asia and Australia/New Zealand (ANZ) and did not differ with age. There was no significant relationship with diabetes, glucose or total cholesterol (p > or = 0.18). Smoking, alone, showed different effects in the two regions, possibly due to the relative immaturity of the smoking epidemic in Asia. In ANZ, the multiple-adjusted hazard ratio for an extra 5 cigarettes per day was 1.12 (95%CI: 1.03 - 1.22), whereas in Asia it was 0.77 (0.56 - 1.05). Body size is an apparently important determinant of prostate cancer in the Asia-Pacific. Evidence of an adverse effect of smoking is conclusive only in the predominantly Caucasian parts of the region.