We describe in this report a unique cDNA clone isolated from a cDNA library of the human hepatoma cell line PLC/PRF/5. The clone which was isolated by using a hepatitis B virus (HBV) hybridization probe consists of HBV DNA sequences flanked by cellular sequences on either side. 5' flanking sequences are homologous to a nuclear integrate of the mitochondrial gene URF4 (1) and are in antisense orientation with respect to the viral DNA. The 3' sequences are homologous to the flanking sequences in the previously described genomic PLC/PRF/5 clones pAL10.5 and pAL10.7 (2), or clones AL26 and AL26a, respectively (3). Nucleotide sequencing and hybridization data suggest that the mRNA from which the cDNA was derived was spliced and could have been transcribed from one of the above-mentioned integrates. Consensus promoter sequences located on the antisense strand of the mitochondrial URF4 and predicted to lie 5' to the HBV sequences might have allowed the expression of the transcript.