Abstract
A correlated electromyographic and histological study was made in cases of classical rheumatoid arthritis to determine the incidence of polymyositis. No specific abnormality was detected in 18 cases not on corticosteroid therapy, suggesting that polymositis is an unusual complication. Cases (9 of 16) on moderate corticosteroid therapy, showed the electromyographic features of myopathy. A new muscle biopsy technic is described.