Transfection of chimpanzee liver cells in vivo or in vitro with cloned HBV DNA induced typical hepatitis B in the inoculated animal. Intravenous inoculation of a 1000-fold greater dose of the same cloned HBV DNA did not induce infection or disease. The experiment proved that cloned HBV DNA is fully functional and that the nick gap structure, proteins covalently linked to the HBV genome, or any other HBV particle associated protein are not needed for initiation of virus replication.