Among 329 patients with rheumatoid arthritis treated with D-penicillamine (DP), we found 4 cases of polymyositis. This incidence was significantly higher than the expected coincidence of rheumatoid arthritis and polymyositis/dermatomyositis or than the presumed frequency of this complication among patients treated with DP. In the present report, we summarize and discuss the clinical findings in DP-induced polymyositis/dermatomyositis in our patients and others described in the literature.