ANTIBACTERIAL agents do not cure bacterial infections; rather, they allow the natural defence mechanisms of the body, both immune‐mediated and innate, to eliminate infection. They work most effectively when the causes of infection are controlled. In rational antibacterial therapy the use of antibacterial agents is restricted to situations where they are essential and have the most realistic chances of success. This article largely concerns antibiotic therapy in the context of surgical chemoprophylaxis. It highlights general points applicable to all involved with the use of antibacterial agents and also briefly considers the role of these drugs in the management of patients with indwelling drains and catheters.