In a series of 100 adult patients with definite rheumatoid arthritis of at most 3 years' duration and with no previous penicillamine, gold or systemic corticosteroid treatment, 50 patients were treated with D-penicillamine and 50 with gold for one yar. The dose of penicillamine was 600 mg daily. Sodium aurothiomalate was given 50 mg weekly up to a total of 13 mg/kg and thereafter 50 mg once a month. In both treatment groups a statistically significant decrease in the number of painful and/or swollen joints, an increase in haemoglobin and a decrease in ESR, serum ceruloplasmin-, alpha1-acid glycoprotein-, IgG-, IgM- and IgA levels was observed. All the changes in these clinical and laboratory tests were of the same degree in both treatment groups. In the penicillamine group 12 out of 20 seropositive patients became seronegative and in another 5 the Waaler-Rose titre dropped clearly. In the gold group, 7 out of 16 seropositive patients became seronegative, and the Waaler-Rose titre dropped in another 5. An equal increase in the number of eroded joints in hands and toes was seen in the penicillamine and the gold group. Penicillamine was discontinued because of side effects in 13 patients (26%), and gold treatment in 15 (30%). Proteinuria and/or haematuria were the most common causes of discontinuation in the penicillamine group.