We investigated the compliance of emergency department health care workers with barrier precaution policies adapted from the Centers for Disease Control's "Recommendations for Prevention of HIV Transmission in Health-Care Settings." One hundred sixty-nine health care worker encounters with 97 patients were observed. One hundred one observations were of noncritical ED patients undergoing IV catheter placement (35) or phlebotomy (66). Sixty-eight observations involved cardiac arrest or critical trauma patients. Observations in this latter group were of the use of needles, 22; physical examination, 18; patient handling, 17; endotracheal intubation, eight; and Foley catheter placement, three. For noncritical patients, only 52.5% of providers wore gloves for phlebotomy or IV catheter placement. For critical patients, gloves were worn by health care workers as follows: needle use, 64%; physical examination, 72%; intubation, 88%; physical handling of patients, 76%; and Foley catheter placement, 100%. Gowns, masks, and protective eyewear were used in encounters with critical patients by 28%, 1%, and 18% of workers, respectively. We conclude that there currently is a low rate of compliance with universal precaution policies by ED personnel.