It is unclear whether serum ALT levels or virological characteristics of hepatitis C virus(HCV) including HCV genotypes and HCV RNA titers, can reflect the degree of histological injury in chronic hepatitis C. The aim of this study was to investigate the relationships between the levels of histological damage and serum ALT levels, HCV genotypes or circulating HCV RNA titers in chronic hepatitis C. A total of 56 patients underwent liver biopsy and the histological activity index (HAI) was evaluated by Knodell's scoring system. HCV genotype by RT-nested PCR and HCV RNA quantitation by competitive RT-PCR were performed. Thirty-four patients were infected with HCV genotype 1b, 20 patients with genotype 2a, and 2 patients with undetermined type. Serum ALT levels were not positively correlated with total HAI score or HCV RNA titers, but showed a linear correlation with scores of piecemeal necrosis (r=0.32, p<0.05) and portal inflammation (r=0.27, p<0.05). HCV genotype had no significant correlation with RNA titers, HAI score or with serum ALT levels. Also, no statistical relationship was seen between HCV RNA titer and HAI score. These results suggest that liver histology is essential to evaluate the severity of chronic hepatitis C precisely.