The aim of this study was to evaluate wether the risk for developing schizophrenia is increased in individuals with Obstetric Complications (OCs) at birth. The sample comprised 47 consecutively admitted male patients with the diagnosis of chronic schizophrenia, according to DSM III-R criteria, and their 51 brothers. An obstetric history was obtained by interview to the mothers and the midwife protocol by Parnas et al. (1982) was used to quantify presence and entity of OCs. The hereditary component was held constant by using healthy siblings as controls. We chose brothers only, so to exclude the possible confounding effect of the gender factor. Odds ratios for the effects of maternal age, birth order, birthweight and OCs were calculated using logistic regression. The only factors found to have a significant effect on the risk of schizophrenia were the measures of OCs at birth. We used three categories of total score (ts) of OC severity (ts=0, ts=1 and ts>2) which yielded odds ratios of 1, 2.78 and 3.02. Our results suggest that OCs can play a important role in increasing the risk for the development of adult schizophrenia, where the hereditary component is constant; this seems to confirm the importance of non-genetic factors, such as OCs, in the subsequent development of the illness.