Compared the rate and degree of consanguinity in the parents of 143 schizophrenics (aged 16-70 yrs) who satisfied the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) diagnostic criteria, and the same number of controls matched for age, sex, and socioeconomic status (SES). A family history of disorders suggestive of schizophrenia in the offspring of consanguineous parents who were schizophrenic was compared with the incidence of a similar history in the schizophrenic offspring of nonconsanguineous parents. There was no significant difference in the former, but there was in the latter. This finding supports the theory of a familial tendency towards schizophrenia and the possibility of recessive or a multigene pattern of inheritance.