Operating room management decisions on the day before and on the day of surgery are well understood and effective at reducing patient waiting from scheduled start times. We investigated monitoring each surgeon's patients' mean tardiness. Discrete-event simulation shows that mean tardiness can be monitored and accurate confidence intervals obtained using 6 four-week periods of data. As mean tardiness was primarily determined by the scheduled workday's duration, the duration needs to be controlled for in benchmarking. There was no need to control for: 1) average OR time; 2) similarity of OR times among cases; or 3) whether cases can start early.