Cryoglobulins were measured in 29 patients (24 female, age 53.8 +/- 9.8 years) with rheumatoid arthritis (70% active). The cryoprecipitate was isolated, characterized and quantified. Cryoglobulinemia, always polyclonal or type III, was found in 83% of patients. The most frequent immunochemical isotypes found were IgG and A. Acrocyanosis was found in 50% and Raynaud phenomenon in 32% of patients with cryoglobulinemia. It is concluded that exhaustive detection of cryoglobulinemia in rheumatoid arthritis demonstrated a higher frequency than previously reported an is important for understanding pathogenesis of the disease.