Dealing with uncertain surgery times in operating room scheduling

•A general model for decision support for the operating room scheduling problem, using integer optimization.•A novel approach to introduce case length uncertainty into the problem formulation.•Use of chance constraints to control uncertainty, showing how these can be implemented in the integer optimization model.•Experimental results, using historical instances, show that this approach improves schedule performance significantly.•The analysis shows the improvement gained if it is possible to add flexibility to physicians' assignment to surgeries.