Newborn rabbits were inoculated with bovine leukaemia virus (BLV). The majority of infected rabbits produced antiviral antibodies. All the seroconverted animals developed symptoms resembling AIDS and died several months after inoculation. The course of experimental infection of rabbits with BLV resembled in many respects the broad spectrum of clinical disorders associated with AIDS induced by HIV. Antibody response to virus proteins was followed by immune deficiency and signs of neuropathy, and the animals subsequently died of opportunistic infections. Virus transmission from infected babies to the mothers by contact was also observed. In some cases the virus was salvaged from lymphocytes of rabbits with the immune deficiency syndrome. The virus-specific sequences were found to be integrated at random in the DNA of haematopoietic cells and of some organs. Slight expression of viral RNAs in lymphocytes was found. Experimental infection of rabbits with BLV can be used in experiments to understand AIDS induction.