The intracellular structure and expression of integrated hepatitis B virus (HBV) DNA in the hepatoma tissue #1707 obtained from an 11-year-old boy were studied. It was found that most of the HBV genome was present in the #1707 DNA. Virus-specific 21S mRNA was also demonstrated by blot hybridization. This is the first direct evidence for the expression of the integrated viral genome in human hepatoma tissue.