Cryoglobulinemic syndrome refers to a systemic inflammatory process that involves small and medium-sized vessels accompanied by multi-organ damage. The aim of the present study was to determine the incidence of cryoglobulinemia among patients infected with human immunodeficiency virus (HIV), hepatitis C virus (HCV) and HCV/HIV co-infection, as well as evaluation of cryoglobulinemia type. The association was evaluated between cryoglobulinemia and clinical symptoms, selected biochemical measures of liver and kidney function, virologic measures, as well as histopathological changes in the liver. One hundred and forty-one patients were enrolled (59 HCV mono-infected, 48 HIV mono-infected, and 34 HCV/HIV co-infected). Cryoglobulinemia was nearly five times less frequent among HIV mono-infected patients (10%) than HCV mono-infected (53%) and HCV/HIV co-infected patients (59%). Cryoglobulinemia was more frequent in patients infected with genotype 1 HCV than genotype 3 (63% vs. 46%, p=0.12). There was a lower incidence of cryoglobulinemia in HIV mono-infected patients treated with antiretroviral drugs (p=0.04). Cryoglobulinemia correlated with ALT activity (p=0.01) and HIV viral load (p<0.001). Symptoms were significantly more frequent among cryoglobulinemic patients than those without cryoglobulinemia (38% vs. 9%, p<0.001). The most common symptoms related to cryoglobulinemia, regardless of cryoglobulinemia type, were fatigue (38%), arthralgia (20%), polineuropathy (18%), and skin lesions (14%). In conclusion, HCV mono-infection and HCV/HIV co-infection, regardless of HCV genotype, are potent stimulators of cryoglobulinemia, with its symptomatic form occurring in about 40% of cases. Effective antiretroviral therapy seems to be protective against cryoglobulinemia development in HIV mono-infected patients.