In this paper we develop a possible notion of short-term value-based reliability for operating an electric power network. As the electric power industry goes through the restructuring process, the operation based on the value-based reliability may be more appropriate than based on the traditional (N-1) security criteria. The value-based reliability requires a framework where the factors to be considered include not only the cost of energy and the cost of generation reserve (and interruptible load contracts) for anticipated contingencies, but also the cost of generation adjustment, and the cost of demand interruption following each actual contingency. In this framework each contingency needs to be evaluated as a stochastic dynamic process since the effect of a contingency depends on the unpredictable time of its occurence. It is shown that the new notion developed here can be useful in analyzing the performance of already functioning market or in designing unbundled markets for energy, reserve and adjustment.