We prospectively studied 684 operations from all surgical specialties to describe the frequency and character of blood contact and exposure during the procedures. Blood contact was defined as percutaneous, mucous membrane, nonintact skin or intact skin contact of patient blood with any member of the operative team. Blood exposure was defined as contact in any of the preceding categories excluding intact skin. Over-all, 28 per cent of the patients had one or more blood contact events that involved 293 operating room personnel. Risk of blood contact was significantly greater for cardiothoracic (p less than 0.001), trauma (p less than 0.003) and obstetric cesarean section (p less than 0.021) procedures when compared with all other procedures. Three services (Ophthalmology, Transplant and Oral Surgery) had no contact events. The remaining nine had rates ranging from 17 to 33 per cent. Eight per cent of the procedures (n = 54) resulted in blood exposure to 63 individuals. Percutaneous exposure occurred in 3 per cent of all procedures. Blood contact events increased with increasing operative time. Blood contact most commonly occurred among circulating nurses (n = 79), anesthesia personnel (n = 65), surgeons (n = 59) and first assistants (n = 49). Despite increased concerns over the risk of occupationally acquired viral diseases, blood contact and exposure continue to be frequent events. Surgeons must assume that all patients are potentially infected and should adopt universally applied standards of behavior to minimize contact with blood.