In patients with chronic hepatitis B and C virus (HBV, HCV) infection, an inverse relationship in the replicative activity of the two viruses has been reported. In the present study the genotype of HCV was evaluated in 34 consecutive cases found with hepatitis B surface antigen (HBsAg) and anti-HCV in the serum, in order to identify its possible influence in determining the pattern of HBV/HCV interaction. Nineteen patients were HCV-RNA positive and could be genotyped: 8 were infected by HCV-1 (3 by HCV-1a and 5 by HCV-1b), 10 by HCV-2, and only 1 by HCV-3. Among these, 3 were HBV-DNA positive, compared to 10 of 15 HCV-RNA-negative patients (P = 0.003), and all 3 were coinfected with HCV-2. Mean alanine aminotransferase (ALT) levels were similar between patients infected with HCV-1 and HCV-2. Among 7 patients with cirrhosis 5 were infected by HCV-2, while 6 of 12 of those without cirrhosis had HCV-1 infection. In conclusion, HBV replication was inhibited more efficiently by HCV-1 than by HCV-2. Cirrhosis was frequently found in patients with dual HBV and HCV-2 infection.