Each year, approximately 2 million people in the United States experience acute coronary syndromes related to thrombosis and ulceration of atherosclerotic plaque within a coronary artery. The case of Mr C, a 43-year-old man with non–ST-segment elevation myocardial infarction, which is most often caused by subtotal thrombosis, illustrates the complex decision-making process involved in selecting treatment for each patient and in determining whether invasive procedures are warranted. Cardiac catheterization is performed in moderate- and high-risk individuals to define the extent of disease so the proper strategy—medications alone, percutaneous revascularization, or coronary artery bypass graft surgery—can be selected. Medications to disrupt platelet function as well as the coagulation system are used. Treatments are designed to minimize the extent of infarction and prevent reinfarction, thereby improving outcomes. The timing of cardiac catheterization, for whom catheterization is indicated, and the rationale for medication treatment are discussed.