The relationship between marital status and cancer incidence was examined based on 49,191 incident cases aged 30 or over in 1980-1984 by using the data from Aichi Cancer Registry and census data. Although married and widowed people did not show increased incidence for any cancer site studied, single and divorced people showed statistically significantly increased or decreased risks for several sites of cancer. Single males showed an increased risk for esophageal cancer and a decreased risk for lung cancer. Divorced males showed increased risks for cancers of the mouth & pharynx, esophagus, liver, skin and brain. Single females showed increased risks for cancers of the esophagus, stomach, small intestine, liver, pancreas, lung, breast, corpus uteri, ovary & fallopian tube and other female genital organs and a decreased risk for cervical cancer. Divorced females showed increased risks for cancers of the larynx, breast, all parts of uterus and cervix uteri and a decreased risk for biliary tract cancer. The increased risk for breast cancer in single females was more pronounced in older age groups and the increased risks for several sites of cancer in divorced people were more pronounced in younger age groups. These findings may be partly explained by differences in reproductive factors and life style, especially smoking and drinking habits.