- OBJECTIVE: To evaluate the role of mental imagery (MI) in resident training for a complex surgical procedure. DESIGN: Randomised controlled trial. SETTING: Eight centres across Canada and the USA. POPULATION: Junior gynaecology residents who had performed fewer than five vaginal hysterectomies (VH). METHODS: After performing a pretest VH, junior gynaecology residents were randomised to standard MI versus textbook reading (No MI) and then performed a test VH. Surgeons blinded to group evaluated resident performance on the pretest and test VH via global rating scales (GRS), procedure-specific scales and intraoperative parameters. Residents evaluated their own performance. MAIN OUTCOME MEASURE: Change in surgeon GRS score from pretest to test VH. The study was powered to detect a 20% difference in score change. RESULTS: Fifty residents completed the trial (24 MI, 26 No MI). There was no difference in GRS score change via blinded assessment from pretest to test evaluation between groups (mean change 13% [SD 17] versus 7% [SD 14], P = 0.192). There was no difference in procedure-specific score change. There was a significant difference in self-scored GRS score change between groups (mean change 19% [SD 12] versus 9% [SD 11], P = 0.005). Residents also felt more confident performing a VH (mean change 19% [SD 16] MI versus 11% [SD 10] No MI, P = 0.033). CONCLUSIONS: No difference was observed in the surgical performance of residents after MI. Improved resident self-confidence may be attributable to MI or the effect of unblinding on trial participants.