We study the influence of a small transverse radius of curvature ρt on the acoustic or electromagnetic waves propagating on the surface of a convex body by the boundary- layer method. For ρt of order k-1/3, the dependency of the field near the surface along the normal is shown to be, as when ρt is of order 1, described by the Fock- Airy function ω1. However, ρt modifies the attenuation and velocity of the waves, by introducing an exponential term. For ρt or order k-2/3, the normal dependency of the field is described by a new special function, depending on ρt The propagation constant of the wave can be obtained by solving an equation involving this function. © 1994 Springer-Verlag.