Animal studies report equal or greater clinical efficacy with once daily versus multiple daily aminoglycoside dosing; however, results are inconsistent. Extrapolation of these animal data to human data is difficult, since marked variability exists in terms of pharmacokinetic disposition of aminoglycosides. Human data suggest that once daily aminoglycoside dosing regimens are as effective as multiple dosing regimens. However, studies need to be performed assessing the efficacy of once daily aminoglycoside dosing for infectious sites other than intra-abdominal and the urinary tract. In addition, the results of these studies should not be extrapolated to those with renal dysfunction, the immunocompromised, or in patients with aminoglycoside treatment durations of greater than 8 days, as the efficacy of once daily dosing in these patient populations has not been proven. Animal studies assessing nephrotoxicity suggest that multiple daily aminoglycoside dosing results in more frequent or more severe nephrotoxicity compared to once daily dosing. Nine human studies have been published comparing the nephrotoxicity of once daily versus multiple daily aminoglycoside dosing. The majority of investigators have studied nonimmuno-compromised patients with urinary tract infections. Netilmicin has been the most frequently used aminoglycoside, although other agents such as gentamicin, amikacin, and sisomicin have been studied. The most common netilmicin dosage regimen has ranged from approximately 4 to 6 mg/kg administered once daily. Eight of the nine trials performed have documented no significant differences in serial serum creatinine concentrations between once daily and multiple daily aminoglycoside dosing regimens, by the end of the study period. In conclusion, preliminary data suggest that once daily aminoglycoside dosing in nonimmunocompromised patients is equally efficacious and nephrotoxic compared to multiple daily dosing regimens.