Twenty-six patients with myelographic signs suggestive of a spinal arteriovenous malformation (AVM) were examined neurologically and neurophysiologically. By selective spinal angiography it was possible to differentiate between dural arteriovenous fistulae (dAVF 20 patients) and intradural AVMs (iAVM, 6 patients). Initial complaints were nonspecific and variable, mainly consisting of sensory disorders and muscle weakness. Later, patients suffered involvement of both the upper and lower motor neurons. There was a high percentage of lower motor neuron lesions (95%), especially in dAVF patients, which were mostly of widespread distribution and included several myotomes. Electrophysiological examination regularly revealed lower neuron involvement, frequently with pathological spontaneous activity in several myotomes, pathological sensory-evoked potentials after tibial nerve stimulation, but normal sensory conduction velocities of the sural nerve, indicating sparing of the sensory ganglion. Frequently there was a discrepancy between the localization of the dural fistula or angioma and the spinal level responsible for clinical symptoms. This suggests that it may be the inadequacy of the venous drainage system to cope with the blood volume rather than the AV-shunt that is responsible for the symptoms. An early diagnosis is essential, as removal of the shunt before there has been progression to severe neurological deficits (paraplegia) is the only way to ensure a satisfactory outcome.