The clinical and electrophysiological findings in 22 patients with chronic trigeminal sensory neuropathy are described. The main clinical feature was slowly evolving unilateral or bilateral facial numbness sometimes associated with pain and paraesthesiae and commonly with disturbed taste. Nine patients had either systemic sclerosis or mixed connective tissue disease. Of the 13 other patients, 9 had either organ or nonorgan specific serum autoantibodies. Blink reflex latencies were recorded in 17 patients, the commonest abnormality being an 'afferent' defect with modest prolongation of latency. Trigeminal sensory evoked responses were recorded in 14 cases, 6 showing mild prolongation of latencies. It is suggested that the lesion in this type of trigeminal neuropathy is in the trigeminal ganglion or in the proximal part of the main trigeminal divisions. This conclusion is supported by limited pathological data.