An overview of the use of CMR in ACS. Patients presenting with an ACS who have unobstructed coronary arteries on angiography are not uncommon. The differential in this situation is broad and includes myocardial infarction, myocarditis, stress-induced cardiomyopathy, acute pulmonary embolism, cardiac infiltrative disorders, chronic renal failure and other causes of false positives. Professor Choudhary details the utility of CMR in this situation, in addition to conventional NSTEMI and STEMI. The relative merits of imaging protocols are described, including rapid quantitative T1 mapping, T2 weighted and late gadolinium enhancement. Research and potential future clinical tools including molecular cellular functional imaging are also explored.