Bile microflora and its relation to pH of gastric juice was investigated in 225 patients. The isolation rate of microbes from bile of patients with gastritis, duodenitis and duodenal ulcer increased with an increase in the pH value of gastric juice from 1.9 to 6.9. At pH values over 7.0 the isolation rate of the microbes decreased. No such relation was observed in patients with pathological conditions of the hepatobiliary system and intestine. In patients with various diseases of the stomach, the isolation rate of Coli bacteria at pH 1.2-6.9 increased from 20 to 51.5 per cent and at higher pH values it decreased. At higher pH values of gastric juice the composition of microflora isolated from bile was more diverse. Thus, in patients with hypo- and achlorhydria there were isolated Proteus, P. aeruginosa, Candida and associations of various microbes. The isolates were characterized by a relatively low sensitivity to antibiotics.