Ethanol embolization is sufficient to eliminate or improve symptoms of arteriovenous malformations (AVMs) in a high percentage of patients, but with substantial risk of minor and major complications. Inadvertent embolization must be avoided by superselective catheterization or direct puncture of the nidus. According to the angiographic morphology of the nidus, AVMs of the trunk and extremities can be classified into four types: type I (arterio-venous fistulae), type II (arteriolo-venous fistulae), type IIIa (arteriolo-venulous fistulae without dilation of the fistula), and type IIIb (arteriolo-venulous fistulae with dilation of the fistula). The described angiographic classification provides considerable information concerning the characteristics of AVMs in the body and extremities, the optimal therapeutic approach, and the likely therapeutic outcome.