An arteriovenous malformation (AVM) consists of one or more arteries that drain through one or several small openings directly into one or more veins. The capillary system between arteries and veins is missing. The natural history of an unruptured AVM demonstrates a 1-2% bleeding rate and once ruptured a 2-4% annual risk of rebleeding. There is a risk of dying of AVM up to 1% per year, a 1% annual risk of developing de novo epilepsy, and a 1% chance of disability per year. Small AVMs are more likely to rupture than large AVMs. The goal of treatment is complete obliteration of the malformation. The risk of surgical treatment depends mainly on its size, location and drainage pattern. Size and angioarchitecture determine the risks of embolotherapy and radiotherapy. AVMs in Spetzler-Martin grades I-III should be treated by microneurosurgery or a combination of embolotherapy and microneurosurgery. They can be excised with low surgical mortality and morbidity. For AVMs in Spetzler-Martin grades IV and V staged treatment approaches such as embolotherapy followed by surgery or radiotherapy should be considered. Rarely is embolotherapy or radiotherapy alone indicated. There are AVMs in Spetzler-Martin grades IV and V that may be inaccessible for surgical or any other treatment, and that should be left alone. Prospective randomised trials on the optimal management of AVMs are lacking. All our knowledge on AVMs stems from open series and indirect comparisons.