Hepatitis C virus (HCV) infection is associated with immune-complex mediated disorders, including Type II mixed cryoglobulinaemia. Mixed cryoglobulinaemia is itself a low-grade B-cell lymphoproliferative disorder which may progress to non-Hodgkin's lymphoma (NHL). Studies from Europe and Asia have found a prevalence of hepatitis C virus infection in non-Hodgkin's lymphoma patients as high as 34%. Other viral infections are also associated with non-Hodgkin's lymphoma. We speculated that non-Hodgkin's lymphoma patients in the midwestern USA would have an increased prevalence of hepatitis C infection. We tested 73 patients with NHL and 20 controls with Hodgkin's disease for anti-HCV antibodies by EIA-2. Only 1/73 patients and no control subject was positive for anti-HCV. The anti-HCV positive patient had no identifiable risk factors for hepatitis C, and ALT was persistently normal. HCV-RNA testing by RT-PCR was negative. Thus, none of 73 non-Hodgkin's lymphoma patients could be confirmed to have hepatitis C infection. In a second part of the study, of 438 patients with HCV infection followed an average of 28.1 months, only one patient developed non-Hodgkin's lymphoma. We conclude that in our population, non-Hodgkin's lymphoma is not associated with hepatitis C virus infection. Based on these results and review of the literature, there are marked regional differences in the prevalence of hepatitis C infection in Non-Hodgkin's lymphoma.