The sense of smell is greatly underappreciated at present, and olfactory dysfunction can lead to significant impairment of quality of life. Disorders of the sense of smell can be frustrating for the patient as well as physician. Several different pathophysiological mechanisms, such as sinonasal disorders, upper respiratory infection, head trauma, aging, and toxic chemical agents, can contribute to olfactory dysfunction. Commercially distributed smell tests and newer imaging studies have made diagnosis and measurement of the degree of olfactory dysfunction available, with implications concerning possible treatment. In this paper, the author reviews the anatomy of the olfactory system, means for clinically assessing its function, and major olfactory disorders with possible management.