A general reverse-flow relation is obtained within the framework of second-order (in surface deflection) supersonic flow theory. From this it is shown that the second-order increment in the drag of an arbitrary quasicylindrical body can be expressed as surface and volume integrals of the first-order solutions corresponding to forward and reverse flow past the body. Analogous results are obtained for second-order transverse forces and moments on an arbitrary quasiplanar wing, except the first-order reverse flow must correspond to certain zero-thickness wings. Other similar results are possible. Thus, second order aerodynamic forces on bodies may be obtained from first-order solutions by quadrature. It is also shown that the reverse-flow integral relation can yield the pressure distribution on the surface by inversion of an integral equation constructed therefrom. It is thought that these results should be particularly useful for the Mach number range between that of linearized theory and that of full hypersonic small-disturbance theory. (Author).