Pseudomonas aeruginosa is an opportunistic pathogen commonly associated with nosocomial infections. Because of the limited efficacy of chemotherapy against pseudomonas infection, this study attempted to evaluate the protective effects of pseudomonas vaccine(serotype F) in the animal experiment for the potential applicability of the vaccine to the clinical situations. Single, twice, thrice vaccinated and control ICR mice having experimentally induced burns(second degree, 20% of total body surface) on the dorsal surface were infected immediately or 24 hours later after burn with variable inoculum size(3×10⁸ or 3×10⁷ cells) of homologous(serotype F) and of heterologous(serotype B) P. aeruginosa into burned area or into peritoneal cavity. Following results were obtained : 1) The pseudomonas vaccine was definitely protective against the homologous P. aeruginosa infection. 2) The pseudomonas vaccine was partly protective against the heterologous P. aeruginosa infection. Therefore, in order to apply these results to clinical situation to prevent P. aeruginosa infection, it is suggested that representative serotypes of P. aeruginosa prevalent in the environment be included in the vaccination program.