Twelve cDNA clones of Japanese hepatitis C virus (HCV) have been isolated from liver tissue of a single non-A, non-B hepatitis patient. These clones represented the non-structural domains of HCV. The degree of substitution in the nucleotide sequences and deduced amino acid sequences between these clones was 9.5 and 7.7%, respectively. This high level of substitution suggested that repeated infections of different HCVs may have occurred in the patient.