WIAS-TeSCA (Two- and three-dimensional semiconductor analysis package) is a program system for the numerical simulation of charge transfer processes in semiconductor structures, especially also in semiconductor lasers. It is based on the drift-diffusion model and considers a multitude of additional physical effects, like optical radiation, temperature influences and the kinetics of deep (trapped) impurities. Its efficiency is based on the analytic study of the strongly nonlinear system of partial differential equations (van Roosbroeck), which describes the electron and hole currents. Very efficient numerical procedures for both the stationary and transient simulation have been implemented in WIAS-TeSCA.