By digestion with HindIII restriction enzyme, a human hepatocellular carcinoma was shown to contain only 2 hepatitis B virus (HBV) DNA inserts. Both HindIII fragments (8 and 16 kb) were molecularly cloned and the structures of HBV DNA and adjacent host sequences were analyzed. One clone (lambda YH 8) contained part of pre-S(I) through the entire S gene and the other (lambda YH 16) had the middle section of the S to the end of X gene of HBV DNA. No gross rearrangements were observed in either HBV or cellular DNA sequences in lambda YH 16 clone. However, the 8 kb HindIII fragment was considered to be amplified together with flanking cellular sequences. Furthermore, the HBV DNA was integrated into cellular genome at the Alu repeated sequences in lambda YH 8.