- A formal analysis of Gortler-type instability is presented. The boundary-layer and disturbance equations are formulated in a general, orthogonal, curvilinear system of coordinates constructed from the inviscid flow over a curved surface. Effects of curvature on the boundary-layer flow are analyzed. The basic approximation for the disturbance equations is presented and solved numerically. Previous analyses are discussed and compared with our analysis. It is shown that the general system of coordinates developed in this analysis and the correct orderof- magnitude analysis of the disturbance velocities with two velocity scales leads to a rational foundation for future work in Gortler vortices. 1982 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.