Background:The Bonfils intubation fibrescope (BIF), a rigid, straight and reusable fibreoptic device, is being used increasingly to facilitate endotracheal intubation after direct laryngoscopy has failed. We tested the hypothesis that, with the BIF compared to direct laryngoscopy, the rate of failed endotracheal intubation could be reduced in patients with a difficult airway, simulated by means of a rigid cervical immobilization collar.Methods: Seventy-six adults undergoing elective gynecological surgery under general anesthesia were randomly assigned to have endotracheal intubation, facilitated with either a standard size 3 Macintosh laryngoscope blade, or the BIF. A rigid cervical immobilization collar was used to simulate a difficult airway, by reducing mouth opening and limiting neck extension. If endotracheal intubation could not be achieved within two attempts, the cervical collar was removed, and direct laryngoscopy was performed thereafter, using a Macintosh blade in all subjects. The success rate of endotracheal tube placement was the primary outcome variable. Results: Patient characteristics were similar in the two groups. After neck immobilization, the inter-incisor distance was reduced to 2.6 ± 0.7 cm (Macintosh) and 2.6 ± 0.8 cm (BIF). Tube placement was successful in 15/38 (39.5%) patients with a Macintosh blade, and in 31/38 patients with the BIF (81.6%; P = 0.0003). Time required for tube placement was 53 ± 22 sec (Macintosh) and 64 ± 24 sec (BIF; P = 0.15). Conclusion:The Bonfils intubation fibrescope is a more effective intubating device for patients with immobilized cervical spine and significantly limited inter-incisor distance, when compared to direct laryngoscopy.