Twenty-four patients from India, had juvenile muscular atrophy localized to the upper extremities. The condition characteristically affects young men and is not familial. Atrophy is limited to the hand and forearm muscles, with slow progression for two to three years after which it seems to be stationary. The condition is associated with "tremor-like" movements out of proportion to the weakness. Examination of muscle biopsy specimens shows group 2 fiber atrophy. This syndrome, for which no cause has been described, is benign and self-limiting, unlike most motor neuron diseases, and is distal in upper extremities, unlike Kugelberg-Welander disease. Asymmetrical muscle wasting and preceding febrile illness in some patients suggests an atypical poliomyelitis-like viral disease.