Chronic viral infection has been implicated in the pathogenesis of B-cell lymphoma, and hepatitis C virus (HCV) infects lymphocytes. Chronic infection with HCV may result in B-cell proliferation. Individuals infected with hepatitis C are often co-infected with the RNA virus GB virus type C. Studies from Europe where hepatitis C infection is more common than in North America have shown a high prevalence of hepatitis C infection in patients with B-cell lymphoma. The aim of this study was to establish the prevalence of HCV and GBV-C infection in patients with B-cell lymphoma in an area of low HCV prevalence. One hundred patients with B-cell lymphoma (10 high grade, 46 intermediate grade, and 44 low grade) and 100 controls with nonhematological malignancies were studied. Serum was analyzed for HCV antibodies by third generation enzyme-linked immunosorbant assay, and HCV RNA and GBV-C RNA was analyzed by reverse transcriptase PCR. None of the controls or lymphoma patients had antibodies to HCV. HCV RNA was undetected in 60 out of 100 lymphoma patients tested. GBV-C RNA was detected in the serum of 5 out of 100 (5%) of lymphoma patients and in 3 out of 100 (3%) controls. Hepatitis C and GBV-C are, therefore, unlikely to play a major role in the pathogenesis of B-cell lymphoma in North America.