HCV (hepatitis C virus) chronic hepatitis has become one the most expensive diseases for public health systems all over the world in the past 10-20 years, a real epidemic, the second most frequent, after hepatitis B virus infection. Due to the complex manifestations, one may consider HCV infection as a "systemic" disease. Mixed cryoglobulinemia (MC) is the most common extrahepatic manifestation of HCV infection, but cryoglobulinemic vasculitis (CV) is considered to be relatively sparse although prevalence studies are needed. Presence of serum cryoglobulins is essential for MC diagnosis, but serum levels do not correlate with the disease activity or prognosis. MC can be defined as a B lymphocyte proliferation disease being characterized by polyclonal activation and antibody synthesis. Evolution to lymphoma should be considered continuous but also other infectious, environmental or genetic factors could be involved. The t (14.18) translocation and Bcl-2 activation in B lymphocytes, B cell-activating factor (BAFF), E2-CD81 interaction, immunoregulatory T CD4+CD25(high) + lymphocytes and type III IFNs might play an important role in MC and lymphoma evolution in HCV patients.