Cryoglobulinemia was studied in human immunodeficiency virus-positive, hepatitis C virus (HCV)-positive patients in relation to their CD4 cell count. Cryoglobulinemia was found in 18 (31.6%) of 57 patients: 17 (44.7%) of 38 patients with a CD4 cell count of >or=200 cells/ micro L versus 1 (5.3%) of 19 patients with a CD4 cell count of <200 cells/ micro L (P=.0064). Cell-mediated immunity could, therefore, contribute to the production of HCV-associated cryoglobulins.