The pharmacokinetics of tobramycin and sisomicin in patients after kidney transplantations was studied. A significant variability of the pharmacokinetic parameters of tobramycin and sisomicin under conditions of the changing function of the kidney transplant was shown. This required individual control of the drug serum levels in such patients. Linear correlation between the exponent (beta) and the clearance of endogenous creatinine was observed. On the basis of this correlation a nomogram providing a decrease in the percentage of the errors in determining the dosage intervals was plotted.