Objecive. To elaborate a diagnostic system, permitting to confirm or exclude the diagnosis of an acute cholangitis in patients, suffering biliary ducts obstruction.
 Materials and methods. The wok is based on analysis of clinical, laboratory and instrumental indices in 174 patients, suffering the biliary ducts obstruction (in 18 - with an acute cholangitis).
 Results. The diagnostic system was constructed, taking into account informativity of such indices, as ratio of the segmented and stab neutrophils quantity, quantity of stab neutrophils, bilirubin, a gallbladder wall thickness, quantity of monocytes, leukocytes, the Charcot’s triad presence, the body temperature, level of amylase, the duodenal papilla magna size, quantity of lymphocytes, presence of excluded gallbladder, presence of cholecystectomy in anamnesis, the immobile calculus of duodenal papilla magna, tumor, the eosinophils quantity, as well as the presence of any choledocholithiasis and age.
 Conclusion. The elaborated diagnostic scheme for determination of an acute cholangitis in patients, suffering biliary ducts obstruction, owes high security (≥ 95%), because the part of failed diagnosis did not exceeded 5% and have constituted 2.8%.