Ultraviolet (UV) irradiation (1,537 A) during total hip arthroplasty will effectively reduce risk of airborne bacterial contamination of the operative field. An air sampling study at the operative site compared 28 total hip arthroplasties with UV lights on and 19 operations with UV lights off. The use of UV irradiation significantly reduced the average number of airborne bacteria over the operative site, although the results indicate that the number of airborne bacteria collected at the operative site in each conventional operating room without UV irradiation was quite low. Data confirmed the fact that airborne bacteria are a reflection of operating room personnel and their activities. With UV light, the rate of infection from possible airborne sources was 0.15% for 1,322 total hip patients. Thus, emphasis is now placed on those causes of infection that are not airborne.