Intrinsic chromosomal acetyltransferases involved in aminoglycoside resistance have been identified in a number of bacteria. In Providencia stuartii, a chromosomal acetyltransferase (AAC(2')-Ia) has been characterized in detail. In addition to the ability to acetylate aminoglycosides, the AAC(2')-Ia enzyme has at least one physiological function, which is the acetylation of peptidoglycan. This modification is likely to influence the autolytic system in P. stuartii. The regulation of aac(2')-Ia expression is extremely complex involving at least seven regulatory genes acting in at least two pathways. This complexity in regulation indicates that aac(2')-Ia expression must be tightly controlled in response to different environmental conditions. This presumably reflects the importance of maintaining correct levels of peptidoglycan acetylation. In this review, a summary of data will be presented involving both the physiological and genetic aspects of aac(2')-Ia in P. stuartii.