There is an established association between human immunodeficiency virus (HIV) infection and mixed cryoglobulinemia, as demonstrated in studies mostly conducted before the introduction of highly active antiretroviral therapy (HAART). To assess the impact of the latter on the cryoglobulinemic status in patients with HIV infection, 133 consecutive, unselected HIV-positive patients, from which only 8 (6%) had co-infection with hepatitis C virus (HCV), were evaluated for the presence of cryoglobulins, according to whether they received or not antiretroviral therapy (ART). Patients shown to be cryoglobulin-positive in a previous study were assessed prospectively, after introducing HAART. Cryoglobulinemia was found in 10 (7.5%) of 133 patients:4 (3.9%) of 101 patients receiving ART versus 6 (18.8%) of 32 patients not receiving ART (P = 0.013). When HCV-positive patients were excluded from the analysis, the correlation between cryoglobulinemia and ART remained significant (P = 0.019). Among 11 previously detected cryoglobulin-positive patients, 8 became cryoglobulin-negative after receiving HAART for a mean period of 6.5 years (P = 0.039). Thus, ART seems to decrease the prevalence of cryoglobulinemia in HIV-infected, HCV-negative patients, a finding which provides indirect evidence of the etiologic role of HIV in the pathogenesis of cryoglobulins.