This chapter discusses the critical role of interoperability in integrating person-reported outcome measures (PROMs) and experience measures (PREMs) into healthcare systems. Interoperability ensures seamless data exchange between systems for efficient data collection, analysis, and reporting. Four types of interoperability—technical, semantic, process, and clinical—work across technology, data, human, and institutional layers to enable effective communication. Key standards include HL7 FHIR (Fast Health Interoperability Resources), LOINC (Logical Observation Identifiers Names and Codes), and SNOMED CT (Systematized Nomenclature of Medicine—Clinical Terms). FHIR supports PROMs/PREMs through structured resources like Questionnaire and QuestionnaireResponse, enabling adaptive questionnaires, notifications, and dynamic data capture. Challenges arise due to healthcare complexity, ambiguity in natural language, and system-specific dialects, but using FHIR profiles and standardized coding schemes addresses these issues. By leveraging RESTful APIs, structured data, and adaptive workflows, interoperability allows healthcare providers to minimize duplication, improve data accuracy, and enable better decision-making through robust, scalable systems.