The paper deals with the issue of modeling metal oxide surge arresters for the purpose of numerical analysis of switching and atmospheric overvoltages. The IEEE model, the CIGRE model, the simplified IEEE model (Pinceti & Giannettoni) and the Hiszerez model are considered. The simplified IEEE model is implemented in the EMTP software package, for the case of one medium-voltage and one high-voltage surge arrester, and its operation is (numerically) demonstrated for different forms of induced (atmospheric) overvoltage.