Background: Results of clinical trials are often criticized by low inclusion rate and potential sampling bias in patient recruitment. The aim of this validation registry is to evaluate how far an all-comers design in the context of clinical research can ensure the representation of the true all-comers population. Methods: This validation registry is a prospective international multicentre registry, conducted at 10 out of the total 21 centers, participating in TARGET-AC (registered under NCT02520180). During a predefined four-week period data were recorded prospectively on all PCIs performed in the participating centers, whether or not patients were enrolled in TARGET-AC. Data were collected on patient demographics, angiographic lesion- and procedural characteristics. For patients who were not enrolled in the study, operators were asked to declare the reason for not enrolling the patient, using a single-choice questionnaire. Results: A total of 131 patients were enrolled in the TARGET-AC study during the investigated period (ER group), standing as 20% (range 4% and 54%) of all eligible cases per protocol. In the ER group more patients presented with stable angina (61% vs. 43%, respectively; P <. 001). Whereas ST-elevation infarction was less common (5% vs. 26%, respectively; P <. 001), there was no difference in non-ST elevation acute coronary syndrome (32% vs. 27%, respectively; P = .248). Risk factors and comorbidities did not show any difference between the ER and the non-enrolled (NER) groups, except for greater rate of significant valvular disease in the NER group (12% vs 19%, respectively; P = .037). The NER group presented more thrombotic stenoses than the ER group (20% vs 12%, respectively; P = .040). No difference was found in any other investigated angiographic parameters, like target vessels, bifurcation lesion, severe calcification or chronic total occlusions. Admission during regular working hours and availability of study nurse were associated with markedly higher recruitment rate. Conclusion: Results suggest that TARGET AC was outbalanced for stable patients over primary PCIs as compared to real world. However in terms of risk factors and comorbidities the trial managed to represent the collective of real world clinical practice. Fairly representative cases were included at an average inclusion-to-eligible rate of 20%.