This cohort study is a collaborative effort of 8 institutions. The goal is to establish a large scale cohort that can be followed for 10 or more years to assess the relationship between life-styles and cancer occurrence, and to evaluate the role of environmental exposures in the development of six major sites of cancers(stomach, liver, lung, colorectum, uterine cervix and female breast) in the rural population. Since 1993, 11,304 men and women aged over 35 living in four areas have been recruited. The number of target population is 30,000 persons, which is expected to be successfully recruited until 1999. Each subject has completed a detailed questionnaire on general life-styles, reproductive factors, and agricultural chemical exposures through the interview. Anthropometric measurements with body fat composition and the routine clinical laboratories were examined. For the cancer-free cohort, physical examination by the physicians and serologic tests for hepatitis markers, some tumor markers, and lipid profile have been done, but not all. In order to provide an opportunity to incorporate barious biomarkers of exposure and effect as well as genetic susceptibility, a biologic tissue bank has been established from blood and urine sample(plasma, WBC buffy-coat, RBC clots, and urine supernatant) stored at-70degrees C. Re-examination of changes in exposere to risk factors will be done periodically. Disease occurrence will be ascertained by the active(mainly through diagnosis by physicians) and the passive surveillance(through both death certificate and screening of medical utilization records).