Azlocillin pharmacokinetics was studied after a single intravenous injection of the antibiotic in a dose of 4 g in 20 patients in critical state. To elucidate the causes of significant individual variability of the antibiotic pharmacokinetics observed in the patients, multiple correlation analysis of the main pharmacokinetic parameters i. e. the area under the concentration/time curve, total clearance, steady-state volume of distribution and mean residence time was performed in regard to the "patient factors" such as sex, age, the volumes of transfused liquid, blood, plasma and blood substitutes, hemoglobin levels, erythrocyte count and ESR. Adequate correspondence of the predicted by the "patient factor" values of the areas under the concentration/time curve and the total clearance to the actually determined values was observed. Correspondence of the predicted values to the steady-state volume of distribution and the mean residence time to the actually determined values was satisfactory. A procedure for design of azlocillin individual dosage regimens based on calculating individual clearance by the "patient factors" is described.