The authors present seven cases of apparently isolated spontaneous haematomas of the brain stem detected by computerized tomography (CT). Magnetic resonance imaging (MRI) was performed in all patients, and in three of these on two occasions at different stages of the lesion. Changes in MRI signal according to the moment this examination was carried out (acute, subacute or chronic stage) are described. In two of three patients operated upon the haematoma was found to be due to an occult vascular malformation.