Among new cases of non-A, non-B hepatitis in the United States, 18 percent are positive for GBV-C, and 80% of these patients are also infected with HCV. Amongst patients with HCV, 10-20% have GBV-C RNA in their serum (4). In another report 189 patients with chronic HCV infection were evaluated; 21 (11%) were positive for GBV-C RNA (8). The course of the HCV infection and the response to interferon-alfa were not affected by co-infection with GBV-C. Interferon-alfa led to a decrease in GBV-C RNA titers that was not sustained after the cessation of therapy. Similar findings were noted in another study in which liver biopsies were performed (9). Detailed histopathologic examination revealed no difference between the patients infected with HCV alone and the 15 percent who were co-infected with GBV-C. There have been no studies to date looking at the effect GBV-C, HCV and HIV have on each other.