Aminoglycoside antibiotics are frequently employed in the treatment of serious infections caused by aerobic gram negative bacilli. The use of these potent antibacterial agents is limited by the risks of ototoxicity and nephrotoxicity. Aminoglycosides are excreted by glomerular filtration at a rate proportional to the serum concentration. Impaired renal excretion reduces the rate of clearance from the serum. Utilizing information about aminoglycoside pharmacokinetics, the susceptibility of infecting pathogens to aminoglycosides, and risk factors for ototoxicity, physicians can attempt to optimize the administratioin of an aminoglycoside to maximize the therapeutic efficacy and to minimize the risk of ototoxicity. Periodic assessments of renal function and of aminoglycoside levels in the serum are essential to guide therapy. The otolaryngologist and audiologist must be able to provide information about ototoxicity to medical colleagues using these drugs. They should also be prepared to evaluate and follow patients who develop sensorineural inner ear dysfunction during or after a course of therapy with an aminoglycoside antibiotic.