Antibacterial chemotherapy of cholecystitis and cholangitis is of limited value, i.e. as a supportive measure. Early cholecystectomy and endoscopic-invasive procedures (in the case of cholangitis) are indicated primarily. If causal therapy is not possible long-term suppressive antimicrobial chemotherapy should be tried. Microbiological diagnosis is difficult. Therefore chemotherapy in most cases is done on empirical basis. Blood cultures are useful as well as quantitative cultures of duodenal secretions (in cases of cholangitis only). The most frequently used chemotherapeutics are discussed. Single dose chemoprophylaxis (bactericidal substances) is effective.