We have reviewed our data from 391 patients entered into three prospective, double-blind studies of aminoglycosides and evaluated 127 cases to determine whether aminoglycoside-induced auditory toxicity and nephrotoxicity are independent events. The cases selected for evaluation included all patients treated for greater than 3 days (mean, 7.7 days) who had serial creatinine determinations and were able to cooperate with serial bedside audiograms (250 to 8,000 Hz). Patients received either gentamicin, tobramycin, or amikacin. Drug dosage was altered to keep serum levels 1 h after administration between 5 and 10 mug/ml (gentamicin or tobramycin) or 20 and 40 mug/ml (amikacin). The investigators evaluating auditory toxicity and nephrotoxicity were blind to the aminoglycoside being administered. The incidence of auditory toxicity in the nephrotoxic group (18.2%) was not significantly different from that in the nonnephrotoxic group (15.2%) (P = 0.75; Fisher exact test). There was no statistical difference between the nephrotoxic and auditory toxic groups in patient age, total dose of aminoglycoside, initial creatinine level, duration of therapy, or concurrent use of furosemide or cephalothin. We conclude that aminoglycoside-induced auditory toxicity and nephrotoxicity are independent events when the drug is administered for approximately 7 days and when aminoglycoside levels are maintained within a predefined range.