Seven months following the introduction of an institutional policy mandating compliance with universal precautions (UPs), we observed 127 health care workers performing 1421 interventions on 155 critically ill and injured patients in an emergency department setting in July 1989. Results were compared with a similar study undertaken exactly 1 year previously when UPs were considered as guidelines only. Overall adherence to UPs improved from 44.0% to 72.7% from 1 year to the next. Adherence to UPs improved from 19.5% to 55.7% during interventions on patients with profuse bleeding and from 16.7% to 54.5% during performance of major procedures. Compliance improved from 47.9% to 81.0% for emergency department-based health care workers (residents, attending physicians, nurses, x-ray film technicians). Prehospital care providers, a group not accountable to the institution, remained particularly noncompliant with only 13% adherence. We conclude that mandating UPs as policy with a monitoring component is effective in ensuring a reasonable level of adherence. However, given current barrier technology, achieving appropriate levels of compliance during unscheduled visits by patients requiring immediate attention and rapid intervention remains a challenge.