OBJECTIVES: Develop the Sublingual Immunotherapy (SLIT) Report Card to capture patient-reported local reactions associated with the administration of sublingual immunotherapy, based on the World Allergy Organization’s (WAO) side effect grading system METHODS: Items were drafted based on the WAO grading system. Cognitive debriefing, usability testing interviews, and translatability assessment were conducted. Adults (aged 18+ y), adolescents (aged 12-17 y), and parents/caregivers and their children (aged 5-11 y) participated in two rounds of interviews. A paper version of the SLIT Report Card was tested in Round 1, and both paper and electronic versions were further evaluated in Round 2. Interviews were conducted to confirm appropriateness and comprehension of the instrument’s content and, for the electronic version, ease of completion using the electronic device. A translatability assessment enabled identification and mitigation of potential issues that might arise during future translation and linguistic validation RESULTS: Ten adults, 10 adolescents, and 10 parent/child dyads participated in interviews. In general, subjects interpreted the instrument and instructions as intended, and were able to demonstrate understanding by explaining the meaning of the instrument’s content. However, some adult, adolescent and parent/child subjects were uncertain of, or suggested clarifying, the meaning of certain terms, including tablet, ulcer, taste alteration, uvula, nausea, and itching in the ear. The translatability assessment also identified uvula and nausea as potentially problematic with respect to translation. Subjects were able to use the device and found navigation of the instrument ‘easy’, with only a few minor suggestions made to improve usability. Some wording and formatting changes were made based on subject feedback and the translatability assessment CONCLUSIONS: The SLIT Report Card was refined following best practices for instrument development. The refined SLIT Report Card is appropriate for systematically collecting data on SLIT-related local reactions directly from subjects in a clinical trial setting, based on the WAO grading system.