<p> Anaphylaxis is a potentially life-threatening systemic allergic reaction [1]. We aimed to determine the overall anaphylaxis incidence rate, the incidence of specific causes of anaphylaxis over time, and epinephrine auto-injector prescribing trends in Olmsted County, Minnesota. </p><p> Using the resources of the Rochester Epidemiology Project, a comprehensive records linkage system, we performed a population-based incidence study in Olmsted County, Minnesota, from 2001 through 2010. All cases with a diagnosis of anaphylactic shock and 20% of cases diagnosed with venom/bee sting, food allergy, and medication reactions were manually reviewed. Anaphylaxis incident cases were required to meet the National Institute of Allergy and Infectious Disease / Food Allergy and Anaphylaxis Network (NIAID/FAAN) diagnostic criteria. We also extracted all outpatient epinephrine prescriptions for all Olmsted County residents during 2003-2010 to further explore treatment of anaphylaxis. The sampling faction was accounted for in determining the reported number of anaphylaxis incidence cases. Incidence rates per 100,000 person-years were calculated using the adjusted number of incident cases of anaphylaxis (and likewise the number patients with a prescription) as the numerator and age- and sex-specific counts of the population of Olmsted County as the denominator. The relationships of age group, sex, and year of anaphylaxis with incidence rates were assessed by fitting Poisson regression models using the SAS procedure GENMOD. </p><p> We identified six hundred and thirty-one cases of anaphylaxis (51% male). The median age was 31 years (interquartile range 19-44). Incidence rates differed by year of diagnosis (p&lt;0.001) and by age group (p&lt;0.001). The overall age- and sex-adjusted incidence rate was 42 (95%CI 38.7 - 45.3) per 100,000 person-years. Four hundred and sixty eight cases (74%) of anaphylaxis were evaluated in the emergency department, 71 cases (11%) were admitted to the emergency department observation unit, and 92 cases (15%) were admitted to the hospital. Prescription data showed that the overall age- and sex-adjusted incidence rate of epinephrine prescriptions was 330 per 100,000 person-years (95% CI 320-340). Age-adjusted incidence rates for women and men were 369 (95% CI 354-385) and 288 (95% CI 274-302) per 100,000 person-years, respectively. Prescription incidence rates differed by year of diagnosis (p&lt;0.001), age group (p&lt;0.001), and sex (p&lt;0.001). The incidence rate of outpatient prescription decreased by year during 2003-2005 then became constant during 2005-2010. </p><p> Our master&rsquo;s degree thesis concludes that the overall anaphylaxis incidence rate was 42 per 100,000 person-years during 2001-2010 in the Olmsted County. The food, venom, and medication were the leading causes for anaphylaxis for younger age, middle age and the elderly, respectively. The majority of anaphylaxis cases were treated in the emergency department. The incidence rate of outpatient epinephrine prescriptions, which was 330 per 100, 000 person-years, decreased from 2003-2005 and reached plateau. Our study used updated diagnostic criteria for anaphylaxis and epinephrine prescription to demonstrate the flattening of the incidence. We would like to emphasize the clinicians to be aware of trend of anaphylaxis and supply of epinephrine in the community.</p>