The nonlinear interaction between bulk acoustic waves at a surface to produce surface acoustic waves is analyzed theoretically. In this analysis both the nonlinear wave equation and boundary conditions are rigorously satisfied by the total acoustic fields. Shear‐wave incidence is treated in detail for isotropic fused quartz and numerical cross sections are evaluated for different angles of incidence. Maximum surface‐wave generation is predicted for geometries corresponding to bulk waves, shear or longitudinal, traveling parallel to the surface.