Mycobacterium xenopi (M. xenopi) has been implicated in hospital-acquired infections associated with colonization of hospital water systems. M. xenopi is considered to be as resistant as other atypical mycobacteria, which are known to be resistant to many disinfecting treatments. However, the efficacy of disinfectants on this organism has not yet been studied. Therefore we decided to evaluate its susceptibility to 2% alkaline glutaraldehyde solution, which is commonly used in hospitals. Tests were conducted using five strains of M. xenopi: three isolated from human samples, an environmental strain and a collection strain. We used a membrane filtration assay and counted surviving bacteria before and after several exposure times (5, 15, 30 and 60 min) with the disinfecting solution. The log10 reduction factor of organisms achieved within 60 min contact ranged from 2.5 to 7.5. This showed M. xenopi to be more resistant to disinfectants than M. tuberculosis or M. smegmatis and suggested that environmental strains may be more resistant to alkaline glutaraldehyde than those isolated from human samples.