Many Emergency Medical Services (EMS) systems have adopted epinephrine auto-injector (EAI) use by Basic Life Support (BLS) personnel, and several states now require that BLS personnel be trained and authorized to use EAIs. The objectives of this observational study were: 1) to examine EMS case definitions of allergy/anaphylaxis, 2) to ascertain the incidence of EMS calls for allergy/anaphylaxis and administration of epinephrine, and 3) to quantify the rate of deaths due to anaphylaxis. Data were solicited by e-mail, mail, and telephone from National Association of State EMS Directors (NASEMSD) members, state EMS offices, and state medical examiner and vital statistics offices. Simple descriptive statistics were used to analyze the data. The following was found: 1) there is no standardization of case definitions among states. Some use the terms "allergic reaction" and "anaphylaxis" in EMS protocols without definition, whereas others provide lengthy, specific definitions, with detailed criteria for epinephrine administration; 2) excluding two outliers at 0.04% and 3.9%, nine EMS system databases totaling over 2.8 million runs contained between 0.34% and 0.82% of runs for allergy/anaphylaxis. Seven of these databases reported on epinephrine administration, with rates between 0.16% and 31.1%, and four of the seven clustered between 8.8% and 14.8%. There was little uniformity in the data provided by seven states on deaths due to anaphylaxis, with rates from 0% to 0.94%. Although limited by the lack of data from many states, roughly 0.5% of EMS runs are for allergy/anaphylaxis complaints, with epinephrine administered in roughly one-tenth of these. State death rates from anaphylaxis vary considerably, with rates from 0% to 0.94% reported.