The value of antibiotics in 302 cases of acute cholecystitis was examined. Antibiotics are valueless in decreasing the incidence of local septic complications, such as empyema or pericholecystic abscess formation. Antibiotics are valuable in decreasing the number of wound infections and the incidence of septicaemia in patients who are at risk. Patients at risk are aged over 60 years or have a debilitating disease which lowers host resistance to infection or already have a septic complications, such as a pericholecystic abscess. Patients who are aged under 60 years and who have uncomplicated acute cholecystitis do not require antibiotics.