Assessing the Anaesthetic Time on Operation Theatre Utilisation and Case Cancellation The time to perform an anaesthesia-related procedure at induction and emergence is often overlooked as part of the operation theatre (OT) utilisation time. This prospective observational study aimed to assess the estimation done by the surgeons and anaesthetists on anaesthesia times and the overall OT utilisation in our centre. This prospective observational study included elective cases from 13 surgical disciplines. The trainees, specialists and consultants from surgical and anaesthesia teams estimated the anaesthesia times separately before the surgical procedures. The actual anaesthesia, surgical, total procedural and turnover durations taken to complete the cases were documented. Operation theatre utilisations of those various surgical disciplines involved in the study were also analysed. We analysed 128 elective cases. The average mean time spent for anaesthesia procedures was 28.4 ± 14.1 min, with the mean induction time was 16.0 ± 9.8 min and the mean emergence time was 12.5 ± 8.6 min. Both anaesthetists and surgeons overestimated the anaesthetic times, but anaesthetists estimated closer to the actual anaesthetic times (r = 0.64 vs r = 0.49, respectively). There was no significant difference in the estimated anaesthetic times between different experience levels. All the surgical disciplines had average OT utilisation exceeding 90%, indicating overutilisation. A total of 12 cases (7.1%) were cancelled. Most cases were cancelled due to exceeded allocated block OT times (7 cases) or unavailability of ICU beds (2 cases). We concluded that OTs exceeding the given OT time is the most frequent reason for cancelling elective surgical cases on the day of surgery.