This paper presents a MATLAB-based Voltage Stability Toolbox (VST) designed to analyze bifurcations, voltage stability problems and nonlinear observability in electric power systems. VST combines proven computational and analytical capabilities of stability and observability theory, symbolic implementation and graphical representation capabilities of MATLAB and its Toolboxes. The motivation for developing the package is to provide a flexible simulation environment for ongoing, research conducted at Drexel University's Center for Electric Power Engineering (CEPE), and to enhance undergraduate/graduate power engineering courses. VST is a very flexible tool for load flow, small-signal and transient stability, bifurcation and observability analysis. To illustrate the capabilities of VST, simulations using the IEEE 14 bus system are presented.