OBJECTIVE : Switching from one specialty to another increases mean turnover times (i.e., interval between the exit and entrance of consecutive patients in an operating room [OR]). We estimate the effect on the mean tardiness of to-follow surgeons from following another surgeon of a different versus same specialty. Tardiness of a case's start time refers to the number of minutes the patient enters the OR later than scheduled; tardiness is 0 min if the patient enters early. Tardiness cause surgeon waiting. There are multiple causes of tardiness, but, most often, the preceding case(s) took longer than estimated. METHODS : 10-year historical cohort study with all surgical cases performed during regular workdays. METHODS : Large teaching hospital. METHODS : Estimated OR end times were calculated using a Bayesian method. Because tardiness is influenced by the estimated case start time (i.e., later starting cases have greater tardiness), tardiness values were adjusted to a 12 noon start time for the 2nd surgeon. RESULTS : The cases of to-follow surgeons in ORs had mean tardiness of 45.1 (SE 0.6) min. When the to-follow surgeon in the OR was of a different versus the same specialty from the first surgeon, the mean turnover time was 7.3 (0.4) min longer (P < 0.00001). However, the mean tardiness was not significantly affected (0.1 min, 95% confidence interval [CI] -2.7 to 3.0 min; P = 0.93). In comparison, if one or more of the preceding cases in an OR was an add-on case, the increase in mean tardiness was 35 min (95% CI 28 to 43 min; P < 0.00001). CONCLUSIONS : OR managers can assure surgeons with afternoon starts that following a surgeon of a different specialty generally will not increase their waiting time. Case scheduling should focus on reducing over-utilized OR time and thus the hours that anesthesiologists and nurses work late.