As demonstrated previously, a "beta particle" fraction isolated from the cytoplasm of PLC/PRF/5 cells contains hepatitis B virus (HBV)-specific DNA. Here, further evidence is provided that the specificity of the DNA for HBV is represented at least by sequences coding for the surface and core antigen (HBsAg and HBcAg). This was shown by two different hybridization techniques. One of them, the technique of Southern, distinguished these hybrid molecules formed from those containing HBV DNA integrated into chromosomes. The HBV-specific beta particle DNA forms two distinct bands separate from the high molecular weight cellular DNA.