The anatomy of the left atrium is reviewed with relevance to various interventional transcatheter procedures requiring manoeuvres within or passage through the left atrium. The component parts of the atrium--the atrial body with a vestibule, appendage, venous component, and the atrial septum--are described with emphasis on their spatial relationships to neighbouring cardiac and extra-cardiac structures. Normal variations are discussed for a better understanding of the anatomy so as to reduce the risk of potential complications during procedures.