LUSH2 is a program for Complex Response Analysis of Soil-Structures Systems by the Finite Element Method. The program finds the complete response of a plane finite element model representing a soil-structure system. The program differs from more conventional finite element programs in that it, in an appropriate manner, takes into account the strong nonlinear effects which occur in soil masses subjected to strong earthquake motions. This is achieved by a combination of an equivalent linear method and the complex response method. The latter method makes it possible to work with different damping in each element and to consider higher frequencies than most other methods of dynamic analysis. The input motion is assumed to be specified as acceleration time histories at a rigid boundary of the finite element model, usually the base, and different time histories may be specified for the horizontal and vertical components of the input motion. The solutions for the two components are found independently but may be added by an auxiliary program, COMBINE, which is included. The basic output is the time history of motion of all nodal points of the system. These time histories may be printed, or plotted as time histories of displacement or accelerations or in the form of acceleration and velocity spectra.