A four-grade classification scheme for intracranial arteriovenous malformations (AVM's) is proposed. Grading is based on the size of the AVM; its location and depth; its arterial supply; and its venous drainage. Each of these aspects is divided into four grades with respect to the difficulty it poses for surgical excision. A description of the grading system and its application is given. This grading scale has been correlated with the operative morbidity and mortality in 100 cases of excised intracranial AVM's. The results show that the higher the grade of AVM, the greater the risk of surgical morbidity and mortality. This grading scale is simple and easy to apply. It can guide neurosurgeons in selecting AVM patients suitable for operation, in determining the best type of operation to perform, and in predicting operative difficulties as well as postoperative results.