The influence of polysaccharides on survival of the capsulated K54 A3 and non-capsulated K54 A3 (0) strains of Klebsiella aerogenes exposed to ozone was investigated. Because it had been shown in this work that bacteria lose approximately half of their polysaccharides when suspended in water, all bacterial assays were performed using exactly the same medium surrounding the cells, so as to create the same ozone demand. Sensitivity of both strains A3 and A3(0) to ozone as tested in the laboratory was not significantly different, although the amount of exopolysaccharides adhering to the cells were five-fold greater with A3 than with A3(0).