Employees of the St. Louis Emergency Medical Service (EMS) reported 44 needlestick injuries during a recent 38-month period, an incidence of 145 injuries/1,000 employee years. New employees, that is, those employed for less than a year, reported 19 (43%) of these injuries. Two employees developed clinically apparent hepatitis B during the study period. These results document a high risk to emergency medical personnel of exposure by needlestick to blood potentially infectious for hepatitis and other pathogens. EMS personnel require early and continuing educational efforts directed toward prevention of needlestick injuries and should be offered hepatitis B vaccine.