The purpose of this review was to determine whether a classification scheme for cavernomas based on the MR appearance is predictive of the natural history of the lesions with particular reference to the risk of haemorrhage. We reviewed the clinical and MR findings in 156 patients with intracranial cavernomas. The dominant or symptomatic cavernoma was graded into three groups according to the appearance of the blood products. The presence of haemorrhage, mass effect and oedema was evaluated. Sixty patients had serial MRs with a mean follow-up of 1.9 years. Subacute haemorrhage with mass effect and oedema was evident on the initial MR in 30 patients (19%). In seven patients follow-up MR showed haemorrhage with mass effect and oedema. Six of these bleeds were in the posterior fossa. The haemorrhages seen on follow-up MR occurred in all three morphological types. Regression was found on follow-up MR in five of the seven patients who initially showed a bleed. In 35% of patients, the dominant or symptomatic cavernoma changed on serial MR. Intracranial cavernomas are dynamic lesions with both active and regressive changes seen on follow-up MR. A classification system based on morphology was not found to be useful in predicting future bleeds. Bleeding rates, based on MRfollow-up, were 10.9% in the posterior fossa and 1.7% in the supratentorial compartment.