The development of infectious diseases and/or inflammation-related complications in postoperative cardiac surgical patient represents a diverse and complex array of clinical scenarios that may impact and complicate the hospital course of this patient population. Infectious diseases are different from other coexisting medical conditions in several respects. First, patients may have coexisting infectious diseases that may impact perioperative care when they present for surgery—these infections may be obviously manifest or occult. Preexisting infectious diseases may be the indication for cardiac surgery, or they may alter the planning, course, and risks associated with a particular cardiac procedure. Second, every patient undergoing surgery is at risk of acquiring an infectious disease during the perioperative period. Patients undergoing cardiac surgery are vulnerable to infections both at the surgical site and where natural defenses are breached, such as the respiratory tract, the urinary tract, the bloodstream, and sites of invasive monitoring. Acquired infectious diseases can be transmitted to other patients and to health professionals in the perioperative period, and healthcare workers themselves may serve as active agents in transmitting infectious diseases to patients.