The combined effect of bile acids and antibiotics on the moderately sensitive and resistant staphylococcal strains was studied. 10 staphylococcal cultures isolated from patients with different pyo-inflammatory diseases were tested for their sensitivity to 5 antibiotics (benzylpenicillin, ampicillin, erythromycin, kanamycin and chlortetracycline). 9 of them were moderately sensitive to the drugs. The combined use of these antibiotics with cholic, desoxycholic , dehydrocholic, glycocholic and choleic acids increased the sensitivity of the staphylococci to the drugs in 87 per cent of the cultures. The same regularity was observed with respect to 15 staphylococcal strains isolated from the patients' bile. The combination of taurocholic acid and streptomycin was the most effective. The combinations of the antibiotics with cholic acid were less effective. The same regularities were noted in the experiments with billicultures tested for antibiotic sensitivity on solid media with the patient's bile. Antibiotics with maximum activity associated with the presence of the patient's bile should be recommended for the treatment of patients with inflammatory diseases of the liver and urinary tract.