The 2.2.15 cells-derived from HepG2 cells transfected with a plasmid containing hepatitis B virus (HBV) DNA secrete surface antigen (HBsAg) particles, nucleocapsids and virions (Proc Natl Acad Sci U S A 1987; 84: 1005–1009). The latter elicit acute hepatitis in chimpanzees (Proc Natl Acad Sci U S A 1987; 84: 4641–4644). We studied the presence of intracellular and extracellular HBV covalently closed circular (ccc) DNA in this culture system by polymerase chain reaction (PCR), kinetically analysed HBsAg and hepatitis B e antigen (HBeAg) released in the culture media by quantitative enzyme-linked immunosorbent assay and quantitated by real-time PCR but HBV DNA from intracellular and extracellular HBV-DNA. HBV cccDNA was found both intracellularly and extracellularly. A significant correlation was seen between the extracellular HBV DNA levels and virus antigens (r = 0.833; P = 0.01 and r = 0.939; P < 0.01 for HBsAg and HBeAg, respectively), whereas there was no statistical correlation between intracellular HBV DNA levels and virus antigen levels (r = 0.024; P = 0.955 and r = 0.177; P = 0.625 for HBsAg and HBeAg, respectively). These data would be valuable in studies of the HBV life cycle and of potential anti-viral agents.