The Cohort of Swedish Men was established in 1997, when all men born between 1918 and 1952 and residing in Västmanland and Örebro counties in central Sweden received a questionnaire concerning diet and other lifestyle factors. Of the 100,303 eligible men, 48,850 (49%) responded to the questionnaire. The questionnaire included items about diet, physical activity, medical history, and lifestyle factors such as cigarette smoking history and use of dietary supplements.