This chapter discusses the diagnosis, evaluation and management of valvular diseases including aortic stenosis (AS), aortic regurgitation (AR), mitral stenosis (MS) and mitral regurgitation (MR). Patients with AS are particularly sensitive to changes in cardiac output due to the pressure gradient across the aortic valve. Evaluation of any valvular pathology begins with the history and physical examination, and paying attention to whether valvular defect has been previously noted. If a new acute AR is discovered, the diagnosis of aortic dissection should be ruled out with a CTA or a transthoracic or transesophageal echocardiogram. Blood culture and antibiotics may be indicated if endocarditis or a perivalvular abscess is suspected. Characterization of valve dysfunction in the emergency department is not imperative if patients are hemodynamically stable. Echocardiography should be considered in patients who are hemodynamically unstable. Acute valvular dysfunction is usually secondary to a precipitating critical problem.