Eighty-five patients with rheumatoid disease were treated with penicillamine, and 69 completed more than one year's treatment. The main reason for discontinuing penicillamine in the 16 patients who withdrew was adverse reaction. The number of adverse reactions, however, declined when patients were given lower maintenance doses of penicillamine. In those who tolerated the drug the results of treatment were good. To prevent side effects the drug should be introduced gradually and maintenance doses should be the lowest which produce a satisfactory response. Urine should be monitored for protein and blood for changes in platelet and white cell counts at frequent intervals throughout treatment.