A series of 112 patients undergoing complete surgical resection of arteriovenous malformations (AVM's) of the brain between 1974 and 1990 were analyzed for complications and 12-month outcomes. The cohort consisted of 44 patients with small AVM's (< 2 cm in diameter), 43 patients with medium-sized AVM's (2 to 4 cm in diameter), and 25 patients with large AVM's (> 4 cm in diameter). There was a 3.6% series mortality rate and an 18% morbidity rate. One of the four deaths was caused by normal perfusion pressure breakthrough. Analysis of logistic regression found that the most important factor influencing the occurrence of complications in this series was AVM size (p = 0.005) and that the occurrence of complications (p < 0.001) and the neurological grade at the time of surgery (p < 0.004) both significantly contributed to the outcome at 12 months. This study stresses the importance of defining complications in terms of rigid criteria when analyzing AVM series in order to allow for a correct evaluation of the risk:benefit ratio of surgery. Furthermore, it emphasizes the need for a separate analysis of the importance of complications upon outcome.