Antibiotic prophylaxis is widely used in orthopaedic surgery although proof of its usefulness is lacking in some areas. The increasing use of joint replacement surgery and fracture fixation means that surgeons must examine the use of antibiotic prophylaxis very carefully. Its usefulness has been well demonstrated in joint replacement surgery although further work is required in traumatic orthopaedics. Additionally further investigation is required into the side effects and cost benefits of prophylaxis.