Objective. To determine the safety and pharmacokinetics of recombinant human tumor necrosis factor receptor (p80) fusion protein (rhTNFR:Fc) administered as a single intravenous (iv) loading dose followed by subcutaneous (sc) maintenance injections twice weekly for one month in patients with refractory rheumatoid arthritis (RA). Methods. Four dose groups were evaluated with 4 patients with RA per group: 3 received active drug and one received placebo injection. After each dose group completed 4 weeks of treatment, the patient who received placebo was allowed to receive the active drug for one month. After these 16 patients completed the study, 3 additional patients received the highest dose and 3 additional patients received the lowest dose in an open label study to obtain more safety data (total of 22 patients treated). Results. There were no serious adverse effects. Drug related events include mild injection site reactions in 4 patients that did not necessitate discontinuation of the drug. There was no clearcut dose response among the treatment groups. At Week 4, there was 45% mean improvement in total pain and total joint scores in patients receiving active drug (n = 12), compared to 22% mean improvement in patients receiving placebo (n = 4). C-reactive protein (CRP) levels decreased substantially in patients treated with drug compared to placebo, 30 vs 13%, respectively. The decrease in CRP was most pronounced in the highest dose group. Conclusion. This initial experience with rhTNFR:Fc fusion protein in RA justifies further evaluation of this agent in a larger placebo controlled trial.