Two variants of cell-free protein vaccine have been prepared from the mixture of 4 P. aeruginosa strains, serovars 02, 06, 07 and 011, and from a single P. aeruginosa strain, serovar 02. The preparation contains proteins with molecular weight ranging from 20,000 to 100,000 and the admixture of lipopolysaccharide in negligible amounts (not exceeding 0.08% of dry weight). The vaccine produces no signs of toxicosis in laboratory animals. The vaccine effectively protects mice challenged with P. aeruginosa of different O-serotypes and stimulates the formation of specific protective antibodies in rabbits.