In an ongoing case-control study in Athens on the etiology of hepatocellular carcinoma (HCC), an analysis was made in order to assess whether HCV genotype 1b is associated with hepatocellular carcinoma (HCC). The HCV genotype was determined in 17 HCC patients, 87 patients with chronic hepatitis C (CHC) without cirrhosis (NC-CHC) and 23 patients with CHC and cirrhosis (C-CHC). HCV genotype 1b was detected in 14/17, 16/23 and 23/87 of HCC, C-CHC and NC-CHC respectively. The age- and gender-adjusted odds ratios contrasting HCC with NC-CHC and C-CHC with NC-CHC were 8.3 and 3.8 respectively. These data strongly support the hypothesis that HCV 1b is a stronger liver carcinogen than other HCV genotypes, probably through increased HCV replication and enhanced liver cytopathicity.