Peripheral neuropathy has been noted as a complication of therapy with perhexiline maleate, a drug widely used in France (and in clinical trials in the United States) for the prophylactic treatment of angina pectoris. In 24 patients with this complication, the marked slowing of motor nerve conduction velocity and the electromyographic changes imply mainly a demyelinating disorder. Improvement was noted with cessation of therapy. In a few cases the presence of active denervation signified a poor prognosis, with only slight improvement. The underlying mechanism causing the neuropathy is not yet fully known, although some evidence indicates that it may be a lipid storage process.