Recently, a new class of agents, the substance P antagonists, has heralded a novel approach for the control of emesis. Aprepitant (Emend, Merck & Co., Inc.), the first of this class, was recently approved by the FDA for the prevention of both acute and delayed chemotherapy-induced nausea and vomiting (CINV). Of interest is the vast array of processes in which substance P is involved such as pain, anxiety, depression and inflammation and the potential wide applicability of substance P antagonists to a number of medical conditions outside of the nausea and vomiting realm. The following review provides an overview of aprepitant including pharmacokinetics, pharmacology and clinical evidence for its use in CINV. A brief discussion of other possible indications for aprepitant will also be presented.