Cystatin-C , A cysteine protease inhibitor , play a vital role in tissue remodeling because it is expressed in vascular wall smooth muscle cells inhibiting elastase secreted by these cells in normal arteries. Cystatin-C has shown low expression in atherosclerotic plaques , which could be a risk factor for ischemic heart events .We aimed in this study to assess prognostic value of admission serum Cystatin-C level in patients hospitalized for acute coronary syndrome (ACS) for occurance of complications and major adverse cardiac events during hospital stay and three months of follow up . This is a prospective, controlled non randomized study. A total number of 75 patients hospitalized in the intensive care unit (CCU) with the diagnosis of ACS are included according to joint of ACC/ESC guidelines 2007 for diagnosis of ACS . A control group of the same number of 75 patients presented by chest pain and coronary heart disease was excluded after hospital admission .