Bioelectrical impedance is a noninvasive method used to determine body composition. Aminoglycosides are broad spectrum antibiotics that have a narrow therapeutic-to-toxic ratio. These agents have traditionally been administered using either population approaches (nomograms or Bayesian methods) or individualised pharmacokinetic monitoring, requiring blood sample analysis. Creatinine clearance is a useful measure of renal function that has been assessed using population approaches or by collecting a 12- to 24-hour urine specimen along with serum creatinine analysis. We investigated the use of bioelectrical impedance to determine predictor equations for the calculation of aminoglycoside pharmacokinetic parameters along with creatinine clearance in 20 noncritically ill patients receiving gentamicin or tobramycin. The bioelectrical impedancederived model was able to explain >70% of the variance for half-life and total volume of distribution of aminoglycosides and >90% of the variance for creatinine clearance. Our model, when compared with a previously published model for gentamicin pharmacokinetic parameters, explained more of the variance for total volume of distribution and total body clearance. Bioelectrical impedance may be a useful tool for aminoglycoside dosing or for the determination of creatinine clearance in noncritically ill patients.