The inactivation of hepatitis B virus (HBV) using two commercially available disinfectants was analysed. Indirect evidence of virus inactivation was obtained by examining the decrease in HBV-associated DNA polymerase and HBcAg activities after treatment with increasing concentrations of disinfectant. Inactivation was accompanied by the irreversible loss of all morphological forms typically found in hepatitis B-positive sera and in particular 42-nm HBV particles were absent. Physiochemical analysis confirmed that the exposure of HBV to either product resulted in the degradation of virus particle structure. Direct evidence of HBV inactivation was obtained by treatment of virus pellets prior to inoculation into susceptible chimpanzees. No evidence of hepatitis B was found in animals receiving treated HBV thereby confirming the suitability of certain disinfectants for the inactivation of potentially infectious material.