The operations scheduling problem in electric power systems is to determine which generating units should be on-line and available for generation at each hour and the associated nominal generation or dispatch. This paper describes the scope of the operations scheduling problem, presents mathematical formulations to the problem, and surveys recent advances in optimization-based solution methods. It is mainly concerned with the shorter term aspects of the problem where the time horizon is of the order of a week. The unit commitment, short-term hydro scheduling, and hydro-thermal coordination problems as well as solution methods are emphasized.