We describe two patients with neurofibromatosis, each of whom was found to have an arteriovenous malformation (AVM), an uncommon manifestation of the disease, presenting as an extradural space-occupying lesion in the cervical spine. In one patient the finding of an unsuspected AVM at operation led to massive blood loss; in the other magnetic resonance imaging (MRI) of the neck allowed the diagnosis to be made and the hazard of an operation to be avoided. Solid tumours that may occur in the disease of neurofibromatosis are known to cause neurological deficits as the result of space occupation. We wish to draw attention to another pathological entity which may cause neurological deficits: that of AVMs. We also propose that in the investigation of such a patient MRI be borne in mind as a non-invasive radiological tool, particularly as, hopefully, its cost reduces and its availability becomes more widespread.