Chronic infection with the hepatitis C virus (HCV) may lead to a variety of hepatic lesions from benign inflammation to liver cancer, but the relationships between infection and development of liver disease are poorly understood. To assess whether virus type and load are of pathogenetic importance, 197 Italian carriers with various hepatic lesions were investigated consecutively. Of these, 187 (95%) patients had serum HCV RNA, by reverse transcription-polymerase chain reaction (RT-PCR) with a median level of 1003 x 10(3) genomic equivalents ml-1 according to the branched-DNA assay (b-DNA). One hundred and seven patients (54%) had serotype 1, 22 (11%) had serotype 2, 9 (5%) had serotype 3, 17 (9%) had mixed serotypes and 42 (21%) had no specified serotype. One hundred and thirty four patients were also tested for genotype. The genotype distribution was as follows: 17 (13%) had genotype 1a; 67 (50%) 1b; 29 (22%) 2a; 12 (9%) 3a; 3 (2%) had genotype 1 not classified (NC); 3 (2%) had genotype 2 NC; 2 (1.4%) had genotype 4 and 1 (1%) had mixed genotype 1a + 3a. No virus type was associated with any particular histological diagnosis and all were equally distributed between progressive and non-progressive liver disease groups. Serum HCV-RNA levels were similar in the liver diseased groups. By analogy to hepatitis B, there was no direct correlation between type and level of viraemia and the severity of the underlying liver damage.