Two hundred thirty-eight patients with psoriatic arthritis were entered into a 6-month, multicenter, double-blind trial comparing auranofin and placebo. Polyarthritis (greater than 5 tender joints) was present in 90% of the patients, and 94% were seronegative. Auranofin treatment was statistically superior to placebo treatment, according to physician's global assessment and functional scores. A trend in favor of auranofin treatment was seen for each of the other disease parameters studied. Psoriasis worsened in 6 auranofin-treated patients and in 3 placebo-treated patients. The incidence and nature of other side effects were similar to those observed in similar trials of patients with rheumatoid arthritis. Our observations suggest that the use of auranofin in the treatment of psoriatic arthritis is safe, although its therapeutic advantage over treatment with nonsteroidal antiinflammatory drugs alone is modest.