Disinfectants frequently used in hospitals are presumed to be degraded by bacteria after discharge into the environment. In the present investigation, the degradabilities of several disinfectants such as glutaraldehyde (GA), benzalkonium chloride (BC) and chlorhexidine digluconate (CG) were examined by using three strains of Pseudomonas aeruginosa isolated from activated sludge and acclimatized to the disinfectants. It was found that GA was metabolized to glutaric acid, BC was metabolized to decabutyldimethylamine and toluene, and CG was converted to p-chloroaniline, p-chlorophenol, p-chloroacetoanilide, phenol, aniline, pyrocatechol and pyrogallol. Possible degradation pathways of CG are presented.