BACKGROUND: Obstetric complications have been studied frequently as possible risk factors for schizophrenia. AIMS: To test the hypotheses that individual obstetric complications are most strongly associated with an increased risk of schizophrenia in males, in patients with an early age at first diagnosis and in subjects with a maternal history of psychosis. METHOD: Cases of schizophrenia diagnosed between January 1971 and June 1994 were identified in the Stockholm County In-Patient Register. Controls were matched on age, gender, hospital of birth and parish of birth. Obstetric data were recorded blind to case-control status for 524 cases and 1043 controls. RESULTS: This study did not find any large or consistent effect of gender, age at diagnosis or maternal history of psychosis on the risk of schizophrenia associated with individual complications. CONCLUSIONS: Future studies should examine these effects using a much larger sample that includes patients with schizophrenia and control subjects whose genetic risk of schizophrenia has been assessed accurately.