The association between reperfusion delay and myocardial damage has previously been assessed by evaluation of the duration from symptom onset to invasive treatment, but results have been conflicting. System delay defined as the duration from first medical contact to first balloon dilatation is less prone to bias and is also modifiable. The purpose was to evaluate the impact of system delay on myocardial salvage index (MSI) and infarct size in patients with ST-elevation myocardial infarction treated with primary percutaneous coronary intervention (PCI).