Lymphocyte transformation, production of neutralising antibody, and the development of antirabies IgG antibody were studied in ten healthy volunteers in response to 0.8 ml of human diploid-cell strain (HDCS) rabies vaccine administered on one occasion in divided doses in 8 intradermal (i.d.) sites. All ten volunteers rapidly developed substantial titres of rabies antibody, and eight of the ten had T lymphocytes that were immunologically stimulated by HDCS rabies-virus antigen. Postexposure treatment with 0.8 ml of HDCS vaccine given at 4 i.d. sites completely protected fourteen rabbits from death by street virus. The results suggest that in developing countries patients could be protected with small volumes of potent tissue-culture vaccine administered intradermally shortly after exposure.