This report documents the work of the IEEE PES Task Force on Test Systems for Voltage Stability Analysis and Security Assessment. The report starts with a short introduction about the motivation and the scope of the work. Next, the models of respectively the Nordic and the RVS test systems are presented in detail, together with a sample of long-term dynamic simulations of their responses to large disturbances. Appendices are devoted to complementary analyses and simulation results obtained with other time-domain simulation software. The system data and a sample of representative outputs will be available on a Web site maintained by the Dynamic Security Assessment Working Group of the Power System Dynamic Performance Committee (please refer to http://ewh.ieee.org/soc/pes/psdpc/index.htm for more information).