With an approximately 50% prevalence rate, medication nonadherence is a significant healthcare challenge that increases the risk of potentially avoidable adverse events and associated costs ranging from $949 to $44 190 per person annually. The ISPOR Medication Adherence and Persistence Special Interest Group conducted a systematic literature review (SLR) in 2023 to evaluate measures used in assessing medication adherence enhancing interventions (MAEIs). The findings revealed that although medication adherence and clinical outcomes were frequently measured, economic and patient-reported outcomes were underexplored. Importantly, the SLR also highlighted the need for consensus-based criteria to assess MAEIs.