Microscopic examination of native bile and smears stained with the Gram procedure rapidly provided information on the presence of bactericholia and the necessity of antibacterial therapy prior to closing of the postoperative wound in accordance with the drug spectrum. Determination of the phagocytic and bactericidal activity of the bile leukocytes was a significant adjuvant to routine microscopic examinations, whereas evaluation of the average cytochemical coefficient and phagocytosis intensity was an important factor in prognosis of postoperative pyoinflammatory complications. Gram-negative bacteria were the predominating causative agents of acute cholecystitis and cholangitis (89 per cent). Among them Escherichieae, Klebsielleae and P. aeruginosa were isolated most frequently (32.4, 31.1 and 16.4 per cent, respectively). Amikacin, tobramycin, sisomicin, gentamicin and cefotaxime showed the highest activity against the above pathogens. However, comparative analysis of the antibioticograms revealed differences in antibiotic sensitivity of separate bacterial species.