Two groups of patients with polymyositis have been followed for approximately 3 years. One group was treated with prednisone alone and the other with prednisone plus azathioprine. Although the polymyositis of both groups has improved, no statistically significant difference was noted at the end of 3 months, as previously reported. Longer followup, however, has shown that the group given prednisone plus azathioprine has improved more with respect to functional disability; this group also requires less prednisone for disease control.