Propofol has been established as a reliable method for sedation in flexible bronchoscopy. There are no data comparing propofol administered as intravenous boluses versus continuous infusion. 702 consecutive patients undergoing flexible bronchoscopy were randomly allocated to receive intravenous propofol using either an intermittent bolus technique or a continuous infusion. The primary end-point was the number of adverse events assessed at the end of flexible bronchoscopy and at 24 h. The number of any adverse event was similar in both randomised groups (219 versus 211, p=0.810). There were complications in eight cases (seven major bleedings, one respiratory failure). As compared with the bolus group, the amount of propofol required was significantly higher in the infusion group (226 ± 147 mg versus 308 ± 204.8 mg, p<0.0001). In a multivariate regression model, this difference remained significant independent of the duration and the interventions performed during the procedure. The duration of bronchoscopy was significantly longer in the infusion group (median 14 (interquartile range 9-24) versus 17 (12-27) min, p<0.0001). Propofol continuous infusion is as safe as bolus administration; however, it is associated with higher propofol requirements and a longer duration of the bronchoscopy.