Eight months after sustaining a reversible left motor hemisyndrome, predominantly of the arm, a 47-year-old man known to have hereditary haemorrhagic telangiectasia (Osler's disease) again developed neurological symptoms (headache, vertigo, unsteady gait) with fever (up to 38.5 degrees C). Clinical features and findings on computed tomography indicated a cerebellar abscess. This was resected because it continued to enlarge despite antibiotic treatment with daily 2 g ceftriaxone and twice daily 0.5 g ornidazole. As another manifestation of Osler's disease further tests revealed an arteriovenous malformation (2.5 x 2.0 cm) in the right upper lobe of the lung, presumably the cause of the cerebral abscess. After wedge resection of the anterior upper lobe segment the further course was without complications.