124 subjects with acute ST-elevation MI who fulfil the inclusion/exclusion criteria and give informed consent to participate in the study will be recruited from patients referred to the cardiac catheterisation laboratories at the Hammersmith Hospital and King's College Hospital. Subjects will undergo primary percutaneous coronary angioplasty (primary PCI) according to standard clinical protocols. Subjects will be randomised to either placebo or EPO at the time of primary PCI. EPO will be given as a bolus of 12ml containing 33,000U over 30 mins via a peripheral vein followed by an infusion of 24ml containing 67,000 U over 12 hours. Placebo will be identical to EPO without the active ingredient. After the PCI subjects will receive standard care on the coronary care unit. An additional 20ml of blood will be taken each day at the time of routine clinical venesection for storage and subjects will have gadolinium enhanced cardiovascular magnetic resonance (CMR) performed before discharge to evaluate infarct size. Follow-up will be performed at 30 days (clinical, ECG and 20ml blood sample) and at 90 days (clinical, ECG and CMR scan and blood sample). The study will end at 90 days and patients will continue with standard clinical care under the direction of a consultant cardiologist.