The aim of this study was to determine whether vaccination of tumor-bearing mice with ribosomes of Candida albicans would result in the induction of protective immunity. Therefore, (BB)F1 mice were inoculated intraperitoneally with the thymoma, EL-4, then immunized with ribosomes purified from C. albicans, and challenged intravenously with C. albicans to assess the protective response. Unimmunized mice, both normal and tumor-bearing, treated in the same manner served as controls. Both normal and tumor-bearing mice developed protective immunity in response to immunization with ribosomes. The protected mice had fewer colony-forming units in their kidneys 3 days after intravenous challenge than the unimmunized control animals, regardless of tumor status. Moreover, all unimmunized mice, tumor-bearing and normal, developed delayed hypersensitivity to the ribosomes, as well as ribosome-specific antibody, both of which were of the same order of magnitude. Therefore, the EL-4 thymoma does not suppress the immune system of mice, and they are capable of responding immunologically in a normal manner to C. albicans.