Blood and imaging biomarkers are tools used in clinical practice to assess infarct size and can be adopted in clinical trials. Among the imaging techniques, CMR represents the most promising technique due to its unique myocardial tissue characterisation, high resolution, and accurate quantitative assessment of myocardial damage. Many agents/interventions have been, and continue to be, investigated in trials to reduce infarct size following STEMI, with the aim of reducing mortality and morbidity. Some have been adopted into clinical care while others are more controversial, and ongoing studies will hopefully determine the best strategy to reduce infarct size in STEMI. Whatever the outcome, such a strategy is likely to involve a combination of pharmacotherapy and interventions. © 2015, BMJ Publishing Group. All rights reserved.