Summary: This paper presents a chronological stochastic method for evaluating the reliability of a generation system, taking operating considerations into account. A sequential Monte Carlo production simulation is used to evaluate the risk level associated with the chronological operation of the system over a year. The approach is based on a combination of a weekly deterministic unit commitment and an hour-by-hour simulation of the system response to unit outages that are not yet known at the beginning of the week. It enables to deal with important aspects in actual system operation: time dependent constraints, energy limited units and start-up delays of thermal units. It can be used to assess the influence of the operating constraints and the operating policy on the reliability level of a generation system. The method is applied to a test case related to a single system and extended to a second text case involving two interconnected systems sharing their operating reserve.