BACKGROUND: Penicillin allergy is the most commonly reported drug allergy and significantly impacts antibiotic prescribing practices and patient safety. Although 10% of the U.S population are reported as penicillin allergic, studies have shown that up to 90% of these patients can in fact tolerate the drug. This mislabeling of approximately 32 million Americans adversely affects antimicrobial prescribing practices and increases health care costs and the risk of antibiotic resistant infections. SIGNIFICANCE/IMPACT: To promote patient safety and improve health related outcomes related to antibiotic use, there is an urgent need to create and implement processes that efficiently de-label penicillin allergy in appropriate patients. The William S. Middleton Memorial Veterans Hospital reports a higher prevalence of penicillin allergy as compared to the general population (22.6% vs 10% respectively), and penicillin allergy is associated with increased use of broad-spectrum antibiotics. Implementing processes to de-label patients misdiagnosed with penicillin allergy will decrease non- concordant antibiotic use, improve patient safety, and advance our goals as a high reliability organization (HRO). INNOVATION: The goal of our pilot study is to apply the Consolidated Framework for Implementation Research (CFIR) to study the contextual factors influencing the evaluation of penicillin allergy in the Veteran population. Knowledge gained will be used to develop an implementation package that identifies, evaluates and de-labels patients inappropriately labeled as penicillin allergic. This effort will address a national patient safety issue of antibiotic resistance and provide a usable intervention to promote the judicious use of antibiotics advocated by the VHA Office of the Inspector General, Infectious Disease of America (IDSA), the American Academy of Allergy, Asthma and Immunology (AAAAI) and the Centers of Disease Control (CDC). We will incorporate feedback from Veterans as well as key frontline physicians, pharmacists, primary care providers and nurses to develop a comprehensive implementation package and data extraction tool to study the impact on key clinical outcomes. SPECIFIC AIMS: We hypothesize that determining and addressing the principal factors influencing access to penicillin allergy evaluation will reduce the number of Veterans designated as allergic to penicillin and in turn, decrease the use of broad-spectrum antibiotics in these patients. We will test this hypothesis with the following aims: (1) Using the CFIR framework, we will study the systems level barriers and key facilitators to evaluating patients with penicillin allergy. The CFIR framework offers a validated implementation science approach that optimizes a mixed methods approach with equal value for qualitative and quantitative data. (2) Develop a penicillin allergy evaluation implementation package that effectively identifies, and de-labels patients misdiagnosed with penicillin allerg...