• This report examines the risk for psychiatric illness in 723 first-degree relatives of schizophrenics and 1,056 first-degree relatives of matched surgical control patients. Diagnoses in patients and relatives were made "blind" to one another, using DSM-III criteria. Information on relatives was obtained from personal interview and/or hospital records. Results were analyzed using two levels of diagnostic certainty and with or without relatives on whom only hospital records were obtained. In all analyses, the risk for schizophrenia was significantly greater (at least 18-fold) in the relatives of schizophrenics v controls. Evidence was also found for an increased risk in relatives of schizophrenics for schizoaffective disorder, paranoid disorder, and atypical psychosis but not for unipolar disorder, anxiety disorder, or alcoholism. As defined by DSM-III, schizophrenia is a familial disorder; however, the increased risk for psychotic illness in relatives of schizophrenics does not appear to be confined to schizophrenia alone.