Objectives: To assess applicability reporting in randomized controlled trials (RCTs) conducted in primary care (PC).Study Design and Setting: We used a random sample of PC RCTs published between 2000 and 2020 to assess applicability. We ex-tracted data related to setting, population, intervention (including implementation), comparator, outcomes, and context. Based on data avail-ability, we assessed whether the five predefined applicability questions were adequately addressed by each PC RCT.Results: Adequately described elements that were reported frequently (O50%) included the responsible organization for intervention provision (97, 93.3%), study population characteristics (94, 90.4%), intervention implementation including monitoring and evaluation (92, 88.5%), intervention components (89, 85.6%), time frame (82, 78.8%), baseline prevalence (58, 55.8%), and the type of setting and location (53, 51%). Elements that were often underreported included contextual factors, that is, evidence of differential effects across sociodemo-graphic or other groupings (2, 1.9%), intervention components tailored for specific settings (7, 6.7%), health system structure (32, 30.8%), factors affecting implementation (40, 38.5%) and organization structure (50, 48.1%). The proportion of trials that adequately addressed each applicability question ranged between 1% and 20.2%, while none RCT could address all of them.Conclusion: Underreporting contextual factors jeopardize the appraisal of applicability in PC RCTs. & COPY; 2023 Elsevier Inc. All rights reserved.