This paper concerns a boundary element method (BEM) for 2D SH‐wave scattering in an elastic layer sandwiched by two half spaces. The BEM is based on the integral equation having a Green’s function for a layer as its integral kernel. Since the Green’s function satisfies the interface conditions, numerical integration in the BEM is necessary only on the surface of scattering objects, thus the computational memory can be saved greatly. On the other hand, numerical evaluation of the Green’s function is critical and burdensome. In this paper, a hybrid ray‐mode representation of the Green’s function given by Kamel is employed. Numerical aspects of the representation are discussed in some detail, and the BEM code with the Green’s function is developed thereafter. As a numerical example, SH‐wave scattering by a cavity in a layer is considered. Some numerical results to investigate the interaction between the cavity and layer interfaces are presented. © 2004 American Institute of Physics