Thirty-eight patients with severe, recurrent herpes progenitalis were treated by immunoprophylaxis with repeated BCG inoculations. Results of the study demonstrated no significant prophylactic benefit of BCG when contrasted to other homologous or heterologous antigens or to control patients receiving placebos. Caution is warranted in the use of homologous vaccines from Germany because theoretically, tumor growth might be enhanced by immunologic means, although the vaccine apparently has no intrinsic oncogenic qualities.