A comprehensive framework for probabilistic steady-state and dynamic security assessment is presented. The time to insecurity is used as the measure of system security. Its probability distribution is obtained from the solution of a linear vector differential equation having coefficients that are expressed in terms of steady-state and dynamic security regions. An illustrative example for a simple system is given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>