More than 20% of U.S. paramedics are exposed to blood each year. Little is known about the circumstances that lead to these exposures. The objective of this study was to describe blood exposure events among U.S. paramedics. A mail survey was conducted in 2002-2003 among a nationally representative sample of licensed paramedics. Eighty percent of needle/lancet sticks involved non-safety devices. A third of mucous membrane exposures occurred even though the paramedic was wearing eye or face protection; in half of the events, the exposures were caused by the patient vomiting, spitting, or coughing up blood; in a third of the events, the patient was being uncooperative or combative. In 83% of the non-intact skin exposures, the paramedic was wearing disposable gloves; the non-intact skin was covered before the call in a third of the events, but the cover did not prevent exposure; 40% of the events occurred when the patient was being uncooperative or combative. These results suggest that blood exposure among paramedics could be reduced through increased use of safety devices and personal protective equipment, improved engineering and design, and increased compliance with Universal Precautions, and that paramedics need techniques for avoiding blood exposure while treating uncooperative or combative patients.