A two-year cohort of children of parapartum mentally ill mothers, born in Stockholm during the mid-1970s, was studied with regard to mortality, hospitalization rate and Well Baby Clinic (WBC) care consumption during the pre-school-age period. The findings were compared with those of matched controls. The index children-especially those of addicts and neurotic or temporarily insufficient mothers-had a higher admission rate and had spent more days in hospital than the controls. The index children tended to have a higher mortality rate than the controls. No significant difference was found in the WBC attendance rates of the index children and the controls. Socially disadvantaged families tended, however, to pay more visits to the WBC than those who were better off. Home visits by the WBC nurse were made more frequently to the index families than to the controls. Failure to appear for regular health checks of the child correlated better with social dysfunction than with mental illness per se in the mother. An adverse social environment, including addiction, seemed to be a separate factor of significant importance, apart from mental illness per se in the mothers, for the morbidity of the children.