A key problem area in recipe design for exothermic batch reactors is the possible occurrence of failure situations, in particular malfunctions of the cooling system. Scenario-integrated optimization has recently been developed in order to tackle these problems rigorously. This paper extends the ideas presented earlier to the on-line solution of scenario-integrated optimization problems. Due to high computational requirements, the problems are formulated only for special cases and on short time horizons. It is shown that the resulting MPC scheme can indeed optimize batch reactor recipes while simultaneously guaranteeing the enforcement of constraints, both for nominal operation as well as for failure situations. A literature example and an industrial polymerization reactor are treated to illustrate these properties. (C) 2003 Elsevier Ltd. All rights reserved.