Bile specimens from sixty-nine patients who had undergone biliary tract surgery or PTC have been subjected to bacteriological study by anaerobic and aerobic techniques. Among 50 specimens from the patients with hepatolithiasis, anaerobes were detected in 74.0%, and aerobes in 98.0%. 11 bile specimens from cholecystolithiasis, only 27.3% anaerobes and 36.4% aerobes were detected. Eight patients with biliary duct tumour had sterile bile. The most common isolated anaerobes was bacteroides and with an average of 1.7 species detected. All bile specimens are mixed infections. The incidence of bacterial infection are higher in the pigmented calcium stone than cholesterol stone. This study showed that metronidazole is the drug of choice in the treatment of anaerobic bile infection.