This chapter describes the bony structures of the proximal humerus.The proximal humerus is often regarded as consisting of fourparts, which assists in understanding function and, more specially,describes the essential parts in reconstruction after fracture or injoint replacement. These are the humeral head, the lesser and greatertuberosity and the humeral shaft. As the gleno-humeral joint hasa large arc of motion but minimal osseous stability, the capsular,ligamentous restraints and dynamic muscular stabilisers are criticalto maintain stability. The humeral head is well vascularised, butprone to avascular necrosis following a fracture.