In an open trial of cryofiltration in rheumatoid arthritis at our institution, 19 patients received 464 treatments; the intensive schedule of ten treatments in 5 weeks was completed in 14 of the 19, and excellent to good clinical response was achieved in ten of these. The combined results demonstrated significant reductions in Ritchie index, morning stiffness, and 50-foot-walk time in the intensive treatment period, as well as significant increases in hand grip strengths. In the maintenance treatment period treatment frequency was individually selected and at less frequent intervals. Changes in clinical parameters were notably less. Although significant correlations were observed between the percent change in clinical parameters and the percent change in biochemical and hematological parameters, no consistent pattern was found. The favorable results of this trial and other uncontrolled trials has led to a two-center double-blind controlled trial of cryofiltration in rheumatoid arthritis that is now in progress.