Aspirin is still the mainstay of antiplatelet therapy in the secondary prevention of coronary artery disease. However certain patients do not benefit from the antithrombotic effects of aspirin. The phenomenon of so-called aspirin resistance can be considered from the clinical and laboratory perspective. A variety of methods have emerged for the laboratory diagnosis of aspirin resistance. None of them is considered ideal as they provide conflicting information with significant inter-individual variability and weak correlation between them. With the mechanisms of aspirin resistance not fully understood and the phenomenon commonly observed in individuals with poor compliance, the existence of aspirin resistance has been challenged. The aim of this review is to present recent data on the impact of aspirin resistance in primary and secondary prevention of coronary artery disease.