Small numbers of organisms can cause orthopaedic implant infections, which give rise to a considerable degree of morbidity and also mortality. The periprosthetic infection rates have been shown to correlate with the number of airborne bacteria within 30 cm of the wound. This is influenced by factors such as the number of operating theatre personnel, their clothing and the type of ventilation system used. Guidance on routine bacteriological monitoring of ultraclean air theatres, based on the Department of Health document Health Technical Memorandum 2025, is discussed. Factors important in minimizing the number of postoperative implant infections such as the use of ultraclean air, ultraviolet radiation, different types of surgical clothing, prophylactic antibiotics and host-related factors are also discussed. The importance of proper scientific investigation into the effectiveness of practical preventative measures in the operating room is emphasized.