The clearance approach was used in the evaluation of the role of renal and biliary excretion in the total elimination of cephothiam from organism of patients after cholecystectomy. Six patients with inserted T-like drain into the choledochus duct and urinary catheter after gall bladder operation received I g cephothiam by stream intravenously during the early postoperative period. The value of renal clearance (= 132.86 +/- 27.35 ml/min) was with one order higher than that of biliary clearance (= 11.54 +/- 9.67 ml/min) and revealed glomerular filtration as the basic mechanism for elimination of cephothiam from the organism of those patients. The value for the sum Clr + Clb = 144.40 ml/min. kre + keb + 1.51 h1-resp. corresponded to the value of the clearance from the central (plasma) compartment, that for kle resp. suggesting that the kidneys and liver were part of that compartment. The high degree of positive correlation between the biliary clearance and biliary flow (r = 0.94, p less than or equal to 0.02) as well as the positive dependence of the biliary excretory rates, biliary excretory rate constants resp X 80, (r = 0.81, r = 0.83 resp) from the biliary flow revealed that the elimination of the drug from the live depends on the volume of the biliary flow. The negative correlation (r = -0.87, p less than 0.05) between the half-life for biliary excretion and the volume of the biliary flow support that presumption.