We have been conducting a cohort study titled the Jichi Medical School Cohort Study (The JMS Cohort Study) since 1992, which is aiming to clarify the risk factors of cardiovascular and cerebrovascular diseases in the Japanese. The baseline data were gathered from April 1992 through July 1995 in 12 rural districts using a legal mass screening system. The total samples were 12, 490 males and females, and the overall response rate for the total population was 63%. The mean ages were 55.2 years for males and 55.3 years for females, respectively. Smoking rates were 50.5% and 5.5%, and drinking rates were 75.1% and 25.0% for males and females, respectively. We also examined the Standardized mortality ratios (SMRs) of the cohort subjects for 7.6 year follow-up period. The SMRs were 0.68 [95% confidence interval (CI): 0.59-0.78] for males and 0.73 (95% CI: 0.62-0.85) for females for the cohort subjects, whereas the SMRs were 1.00 (95% Cl 0.97-1.04) for males and 1.06 (95% Cl: 1.02-1.10) for females for all residents. In this article, we outlined the cohort study and showed general characteristics of the baseline data, and the SMRs of the subjects. We have been following the eligible subjects, and are preparing to show some prospective data regarding cardiovascular and cerebrovascular risks in the near future. J Epidemiol 2002; 12:408-417.