Dermatomyositis developed during treatment with penicillamine in two patients with rheumatoid arthritis. Both were male without a history of penicillin allergy. Eosinophilia was present at the start of their illness, and HLA tissue typing showed the presence of HLA-DR2 in one patient. One patient was retreated with penicillamine and remained asymptomatic after three years of therapy, and the other was able to take penicillamine in a reduced dosage. © 1984.