Operating Room (OR) information systems should manage the OR time, assigned to every surgeon, thereby minimizing the sum of costs of unused OR time and minimizing the costs of elective cases performed outside normal allocated OR time (excess OR-time). The aim of this paper is to illustrate how the introduction of an OR information system influenced daily OR activity performance. Since January 2001, we introduced an OR information system with a visual, airport-like, screen as central part, displaying all scheduled OR activity linked in real-time activity with all OR theatres. For the aim of this paper, we compared all data of OR activity for elective abdominal surgery (EAS) for the first half of 2000 compared to the first half of 2001, after the introduction of our information system. In 2000, 764 elective cases were performed, compared to 815 cases in 2001. For both periods, the total OR time allocated to EAS for this 6 months period was 805 h. For 2000, the total duration of OR activity for EAS was 1044 h 50 min (implicating 239 h 50 min over-time), compared to 1127 h 35 min (implicating 322 h 35 min overtime) for 2001. For 2000, we recorded 147 h 20 min excess time (=exceeding the time limits of OR activity and inducing extra costs) and 46h45min unused OR time. For 2001, we recorded 123 h 04 min excess time and 35 h 21 min unused time. In conclusion, in 2001 we recorded an increase in total OR activity for elective abdominal surgery by 7% in number of procedures and by 8% in total duration. However, in 2001 we recorded a decrease in excess time by 16% (123 h 04 min vs 147 h 20 min), which was for a large part due to a 23% decrease in unused OR time in 2001 compared to 2000 (35 h 21min vs 46 h 45 min). Therefore, the introduction of an OR information system, with a real-time visual display of ongoing OR activity, resulted in a increased performance of OR activity, with more OR procedures performed despite less excess time and less extra costs.