OBJECTIVE The aim of this study was an analysis of complications after surgical treatment of the cerebral supratentorial arteriovenous malformations (AVM), assessment of their clinical sequelae, and attempt to find factors influencing their occurrence. METHODS 88 consecutive patients operated on for AVM in the years 1983-2000 were included in a retrospective study. In all patients microsurgical, selective removal of AVM was performed, without prior embolization. The statistical analysis was carried out by means of exact Fisher test and c2 test. RESULTS Complications in the postoperative period were observed in 45.5%, including short-term deterioration (27.3%) and symptoms present till the day of discharge (18.2%). Mechanisms of deterioration were as follows: significant intraoperative hemorrhage (5.7%), hemodynamic disturbances after AVM removal (20.5%) and resection of AVM in the eloquent area (19.3%). Many variables that may contribute to the complications were studied. Factors increasing the risk of significant intraoperative hemorrhage are: steal effect visible in angiography (32% vs. 10%, p<0.05), intraventricular penetration of AVM (38% vs. 11%, p<0.05). Factors increasing the risk of hemodynamic disturbances are: feeding from the medial cerebral artery (MCA) (31% vs. 8%, p=0.02) and complex venous drainage (32% vs. 14%, p=0.05). CONCLUSIONS The most common causes of postoperative deterioration are hemodynamic disturbances after AVM removal and manipulation in the eloquent area. Hemodynamic disturbances worsened the prognosis significantly, and were the only cause of mortality (3.4%). However, massive intraoperative hemorrhage and operation in the eloquent area did not influence the outcome significantly. Risk factors for intraoperative hemorrhage are steal effect and intraventricular penetration of AVM. Risk factors for hemodynamic disturbances are feeding AVM from MCA and complex venous drainage.