The ability of Klebsiella aerogenes strains isolated from outbreaks of infection, from sporadic infections and from the environment to survive on hands were compared. Considered as groups, the outbreak strains survived best and the environmental strains least well. The possible importance of these observations in relation to outbreaks of Klebsiella infection in hospitals and to heterogeneity of pathogenic potential and transmissibility in Klebsiella aerogenes is discussed.