Surveillance data and case reports substantiate that health care workers are at risk for occupationally acquired infection with blood-borne pathogens. The risk of transmission of blood-borne pathogens to a health care worker depends on the prevalence of blood-borne pathogen infection among patients, the likelihood of transmission of infection per blood contact, and the nature and frequency of occupational blood contacts. In surgical and obstetrical settings, blood contact varies with occupation, specialty, procedures performed, and precautions used. Many contacts appear to be preventable by changes in technique or instrument design and by use of protective barriers. Studies are needed to assess the impact of such interventions.