Background: In Canadian hospitals, which are typically financed by global annual budgets, overuse of operating rooms is a financial risk that is frequently managed by cancelling elective surgical procedures. It is uncertain how different scheduling rules affect the rate of elective surgery cancellations. Methods: We used discrete event simulation modelling to represent perioperative processes at a hospital in Toronto, Canada. We tested the effects of the following 3 scenarios on the number of surgical cancellations: scheduling surgeons' operating days based on their patients' average length of stay in hospital, sequencing surgical procedures by average duration and variance, and increasing the number of post - surgic al ward beds. Results: The number of elective cancellations was reduced by scheduling surgeons whose patients had shorter average lengths of stay in hospital earlier in the week, sequencing shorter surgeries and those with less variance in duration earlier in the day, and by adding up to 2 additional beds to the postsurgical ward. Conclusion: Discrete event simulation modelling can be used to develop strategies for improving efficiency in operating rooms. © 2013 Canadian Medical Association.