0000000000000000. De Rosa Roberta, Morici Nuccia, De Servi Stefano, De Luca Giuseppe, Galasso Gennaro, Piscione Federico, Ferri Luca A, Piatti Luigi, Grosseto Daniele, Tortorella Giovanni, Franco Nicoletta, Lenatti Laura, Misuraca Leonardo, Leuzzi Chiara, Verdoia Monica, Sganzerla Paolo, Cacucci Michele, Ferrario Maurizio, Murena Ernesto, Sibilio Gerolamo, Toso Anna, Savonitto Stefano  Abstract BACKGROUND: Chronic kidney disease is common in patients admitted with acute coronary syndrome and its prevalence dramatically increases with age. Understanding the determinants of adverse outcomes in this extremely high-risk population may be useful for the development of specific treatment strategies and planning of secondary prevention modalities. AIM: The aim of this study was to assess the impact of baseline renal function and acute kidney injury on one-year outcome of elderly patients with acute coronary syndrome treated with percutaneous coronary intervention. METHODS: Patients aged 00 years and older with acute coronary syndrome undergoing successful percutaneous coronary intervention were selected among those enrolled in three Italian multicentre studies. Based on the baseline estimated glomerular filtration rate (eGFR) calculated using the Cockcroft-Gault formula ([(000-age)?×?body weight?×?0.00 if female]/(00?×?serum creatinine)* 0.00 m of body surface area), patients were classified as having none or mild (eGFR ?00?ml/min/0.00 m