Marital status has been identified as an important social factor associated with mortality. Interesting resultswere obtained in the present analyses of the Japan Collaborative Cohort Study. Death of spouse was positivelyassociated with risks of male death from all causes, all cancers, and ischemic heart diseases, compared withmarried status. Divorce or separation was positively associated with risks from all causes among men andwomen, all cancers among women, and single status was also positively associated with risks from all causesamong men and women, and ischemic heart diseases among men. Having large numbers of children was alsofound to be a risk factor.