In a randomized controlled trial at Duke University and University of North Carolina Hospitals, 143 two to six year old children undergoing elective ambulatory surgery were randomized into a control group who received routine preoperative teaching or an intervention group who received an interactive teaching book. Changes in behaviour were measured by a Vernon behavioural questionnaire preoperatively and again two weeks postoperatively. A Global Mood Score was assessed in the preoperative holding area, at arrival into the operating room, and at the time of mask induction. The children in the control group were significantly more aggressive postoperatively than the intervention group (P < 0.05). Children who received the interactive teaching book exhibited higher levels of anxiety on the day of surgery, but fewer behavioural changes two weeks following surgery. Parents in the intervention group reported that preoperative teaching helped their child (87%) and themselves (83%).