In 711 consecutive total hip arthroplasty operations, approximately 80% of patients were followed one to 7 years. Per priman operations outnumbered hips having had previous operations 511 to 200. The incidence of infection was higher in the hips having had previous operations (1.6 vs 3.5%). The overall incidence of deep infection was 16/711, or 23%. Analysis of the influences of operating room environment and preventative antibiotics revealed that there was a marked decrease in the attack rate of deep infection (7.6 vs 0.6%) when the Clean Room, personnel-isolator system, and preventative antibiotics were used. Reduced intraoperative wound bacterial contamination is accompanied by a reduced incidence of sepsis.