Abstract Fifty-eight patients with intracranial AVMs are presented and the influence of size, density and localization of the malformation on the initial symptom (epileptic seizure or haemorrhage) produced by it is examined. Thirteen cases were excluded: 4 had an arterial aneurysm in addition to the AVM, 5 had a meningeal malformation and 4 had neither epileptic seizure nor haemorrhage as symptoms. Of the remaining 45 cases, 23 had epileptic seizure and 22 had haemorrhage as the initial symptom. The volume of the malformation was calculated, using an ellipsoid volume approximation, and the volumes varied between <0.1 and 80 cm 3. Placing the dividing line between small and large at 7 cm 3 (diameter about 3 cm in the X-ray) it was found that 72% of the large AVMs belonged to the epileptic seizure group and 75% of the small AVMs belonged to the haemorrhage group. The compact malformations had a slight preponderance of epileptic seizures as initial symptoms, while the tenuous malformations presented with haemorrhage more often. The frontal malformations had a tendency to produce epileptic seizure as the initial symptom, while all occipital malformations produced a haemorrhage.