Five cases of a chronic neuromuscular syndrome consisted of muscular aching and sometimes burning pain, fasciculations, cramps, fatigue, and occasional paresthesia. The disorder affected the legs and, less commonly, the girdle, trunk, and arm muscles. The symptoms were enhanced by physical activity and were usually improved by rest. Neither muscular wasting nor weakness was found, although the condition was present for an average of 4.7 years and, in one patient, as long as 10 years. Electrophysiologic studies showed motor abnormalities indicative of axonal degeneration and muscle fiber denervation, most marked in the legs. Light microscopy of skeletal muscle and spinal cord in one case disclosed evidence of mild denervation atrophy in muscle, but no loss of anterior horn cells. The findings are compatible with a benign polyneuropathy.