Background - The clinical diagnosis and categorisation of Acute Coronary Syndrome (ACS) has changed repeatedly over the last decade as have routine treatment strategies. Hypothesis - that adverse clinical events following PCI, may be predicted from the identification of markers of risk at the time of PCI. Methods - Informed consent was obtained from 968 patients fulfilling detailed inclusion and exclusion criteria surrounding a diagnosis of ACS requiring PCI. Standard medical ACS care was provided. PCI operators, techniques, methods and any decision to treat followed usual practice. Data collection took place at the time of intervention and during active follow-up. Blood sample were collected at baseline and 4 and 12 hours after PCI, being processed and refrigerated. Platelet function was assessed at baseline using the VerifyNow test method. Results – Data collection was over a median follow-up time of 3.56 years. Patients were aged 27 to 90 years and a majority were male (75%). Angiographic complications occurred in 13.2% and total complications in 17.1%. A majority (844; 86%) had neither restenosis nor subsequent unplanned revascularization. Recurrent ACS was 6.7% for year 1 and 1.8% additionally for each year thereafter. Stent thrombosis was observed in 18 (1.8%) cases. Bleeding occurred in 9% across the entire follow-up period, being greatest in the first 12 months. Platelet reactivity was highly variable and optimal with regard to outcome in the range of 179 to 243 (Platelet Reactivity Units PRU). Cardiac biomarkers were commonly elevated after PCI but procedural MI was very rare. H-FABP at baseline was strongly predictive of outcome. Conclusion – Adverse clinical events following PCI, such as stent thrombosis, bleeding and in-stent restenosis, may be predicted from the identification of markers of risk at the time of PCI, particularly by the use of risk scores, platelet function testing and measuring biomarker levels.