In recent years the trans-sphenoidal approach to the pituitary gland has come into vogue and a study of the surgical anatomy of the sphenoid sinus has become increasingly important in order to avoid many surgical mishaps. Moreover, the sphenoid sinus has complicated relationships and its diseases may and do give rise to a complexity of symptoms. The anatomy of the sphenoid sinus has been described by Ridpath (1947), Dobromylsky and Scherbatov (1966), Davies and Coupland (1967), Simpson et al. (1967), Montgomery (1972), Last (1972), Ballenger (1977), Hamilton and Harrison (1979), and Davies (1980). The present work was designed to study the anatomy of the sphenoid sinus and its surgical applications. Particular attention was focused on the relationships of the sella turcica to the sphenoidal sinuses.