Cardiac troponins (cTn) are considered to be the ‘gold standard’ biomarker for the diagnosis of acute coronary syndrome (ACS); a pathological spectrum which includes cardiac ischemia, angina, myocardial infarction and ultimately cardiac failure. The growing evidence base for the diagnostic and prognostic use of cTn in ACS has resulted in a universal redefinition of acute myocardial infarction (AMI). Recently a number of immunoassays with claims of superior sensitivity have been produced. The analytical and clinical performance of these assays require appropriate evaluation. Sensitive assays can be used for diagnosis in the first few hours after an ischemic episode. Early elevations in cTn are prognostic. A single time point for cTn testing may be useful for rule out, however such a strategy does not detect the rising and falling pattern required for diagnosis as suggested in the universal definition of AMI. The newer assays demonstrate low level cTn positivity in apparently healthy people. In addition, the sensitive assays detect more cTn positive patients who do not have a final diagnosis of ACS. It is unknown if such mild elevations in cTn detected by sensitive assays are of clinical concern. What is certain is that AMI remains a clinical not a biochemical diagnosis and interpretation of cTn concentrations should be made according to the clinical context. This review highlights the development of the sensitive assays, documents their analytical and clinical performance and reviews the usefulness of cTn elevation in non-ACS conditions.