A case of difficult tracheal intubation due to insufficient mouth opening once anaesthesia had been induced is described. At the pre-anaesthetic visit, the 47-year-old female patient had painless restricted mouth opening (two fingers' breadth), dental malpositions, and slight lateral mandibular deviation. Cervical spine movements were normal. She was ranked 3 on the Mallampati scale. The anaesthetic technique preserved spontaneous breathing (induction with propofol 1.5 mg.kg-1 and alfentanil 15 micrograms.kg-1). Manual ventilation was impossible. An oral cannula could not be inserted. As intubation by the normal route was impossible, the retromolar approach had to be used. Several attempts were required for successful intubation by this route. At the end of surgery, the patient was extubated without any difficulties. Postoperative investigations revealed hypertrophic coronoid processes. In this condition, the mandible is jammed by hitting the maxilla, especially when mandibular lifting manoeuvres are used to facilitate manual ventilation and tracheal intubation. Clinical and paraclinical predictors of difficult tracheal intubation seem to be unreliable in such dynamic abnormalities of mouth opening.