ESDU Aero B.S.02.03.01 introduces the concept of dividing the drag into inviscid wave drag@ skin friction drag@ viscous form drag and base drag. ESDU data for estimating skin friction and base drags are available and are referenced. For viscous form drag@ calculation of the inviscid flow about a body shape that includes the displacement thickness of the boundary layer is recommended. For wave drag reference is made to the exact solutions that exist for a right-circular cone and are given in the ESDU data. For more general body shapes@ three principal theories are referenced: linearised theory@ van Dyke's second-order theory and the method of characteristics. A parameter involving the maximum slope of the profile in an axial plane is introduced for assessing the accuracy of results obtained using those theories. The contributions of the forebody@ the afterbody and due to interference of the forebody with the afterbody are treated separately in the ESDU data; the data for forebodies and afterbodies are expected to be accurate over a greater range than would be obtained with linearised theory@ but the interference drag is based on linearised theory. The supersonic-hypersonic similarity law@ which is useful for generalising limited data@ is explained. Brief consideration is given to bodies of non-circular cross section. All the theories mentioned assume supersonic flow everywhere@ that is a sharp nose with attached shock wave. When the bodies have blunt noses the shock is detached and the theories do not apply; semi-empirical ESDU data are referenced for various nose blunting shapes. A bibliography is included.