The single-dose pharmacokinetics of amikacin, netilmicin and tobramycin administered intramuscularly at doses of 7.5 mg/kg amikacin, 2.5 mg/kg netilmicin or 3 mg/kg tobramycin were studied in 30 children with chronic renal failure. Serum amikacin, netilmicin and tobramycin levels were measured by a radioimmunoassay method. The correlation between serum creatinine levels and the half-life of the antibiotics was found to be statistically significant. There were interpatient differences in serum aminoglycoside levels among those with the same serum creatinine levels. Thus, monitoring of serum creatinine and aminoglycoside levels is recommended, especially for those with renal failure, in order to maintain an optimal dosage between toxic and noneffective serum aminoglycoside levels.