EXOPOLYSACCHARIDES (EPS) produced from Pseudomonas syringae pv. tomato, P. syringae davson 973 and P. syringae pv. coriandricola 908 were studied. Mice immunized (i.p.) with bacterial EPS preparations from three strains (divided into 3 days) and in the fifth day, challenged (s.c.) with 1 ml of human pathogen P. aeruginosa 3 to each mouse, all groups of mice showed an increase in total leukocyte counts as well as neutrophil and monocyte numbers if compared with saline control group. Studing the active immunization by purified bacterial EPS on the counts of P. aeruginosa in lungs, spleens and livers of challenged mice revealed the protection of organs against bacteremia. Thus, the immunoprotective characters of the three purified EPSs could be concluded and recommended for prophylactic applications.