Two hundred twenty-three patients with clinical diagnosis of depression requiring hospitalization were divided into categories of suicidal and nonsuicidal and further studied. Considered were three hypotheses of suicidal behavior. It is correlated with: 1, loss of a parent in childhood; 2, social isolation; 3, social degeneration. Social isolation and degeneration did not differentiate the suicidal from the nonsuicidal group, but loss of a parent in childhood was significantly associated with suicidal behavior in depressive illness.