To determine whether the progression of hepatitis C diseases is related to HCV, changes in the proportion of the HCV genotypes and the diversity of the HCV genome were investigated in patients with AH, CH, LC and HCC with LC.Materials and Methods; The subjects were 24, 392, 104, and 84 patients who respectively had AH, CH, LC, and HCC with LC. The serum level of HCV RNA and the proportion of the HCV genotypes were determined and changes in the amounts of HCV clones and HCV RNA were compared. The diversity of the HCV genome at the site of HVR1 was investigated by the PCR FSSA method. The serum level of HCV RNA was determined by the branched DNA probe method.Results; 1) The HCV genotypes, II, III, and IV, accounted for about 70%, 18%, and 9%, respectively, and type I was not detected in groups AH, CH, and Pre-LC. In groups LC and HCC, the proportion of type II was higher, while that of type III was only 3%. 2) The HCV RNA non-detection rate in types II, III, and IV was 37%, 63.7%, and 53.8%, respectively. The amount of HCV RNA detected showed a tendency to be greater in type II. 3) The time interval between the transfusion and the detection of bridging fibrosis was longest (about 28 years) in type IV. In group LC, it was 33 years for type III and 30 years for type II. In group HCC, it was shorter for type II (28years) than type III (35 years). 4) Fibrosis was found to progress in most patients in type II. 5) Patients with and without HCC showed no clear difference with respect to changes in the number of clones. 6) The serum level of HCV RNA increased over time in some patients without HCC, while it was not detected in most patients with HCC.Summary; 1) The HCV genotypes are considered to be related to the progression of of hepatitis C diseases, however, the blood level of HCV RNA and the diversity of the HCV genome at the site of HVR1 showed no clear correlation with this progression. 2) The time interval between the transfusion and the detection of HCC was at least 10 years. The average interval was 28 years in type II and 35 years in type III.