Study objective: Emergency department personnel are at high risk of occupational infection with bloodborne pathogens. The objective of this study was to observe and analyze the use of barrier precautions among ED personnel caring for trauma patients. Methods: This observational study used videotapes of trauma cases seen at an urban Level I trauma center. Study participants were ED and trauma team personnel. Trained observers scored breaks in the use of barrier precautions during the first 15 minutes of 88 videotaped Level I trauma cases. 'Major' breaks were scored when ED personnel performed invasive procedures without gloves, mask, gown, and adequate eye protection. 'Minor' breaks were scored when ED personnel were adjacent to a trauma patient (within 1 m) without wearing these items. Results: We observed 1 or more major breaks in 33.6% of 304 invasive procedures. The most common major break was failure to wear a mask (32.2% of procedures), followed by inadequate eyewear (22.2%), no gown (5.6%), and no gloves (3.0%). We observed minor breaks during 55.5% of 752 patient encounters. Large and statistically significant variations were seen in use rates of barrier precautions among different groups of personnel; surgery residents were most likely to use precautions, whereas attending surgeons were least likely. Conclusion: Compliance with universal precautions is poor in this high-risk clinical setting. These data provide a baseline for measuring the effectiveness of interventions to improve compliance. Videotaped observations are a novel and effective tool in this setting.