In a prospective study (January 1999 to December 1997), 34 patients with 26 mandibular and 20 midfacial fractures were investigated. All the fractures were managed by osteosynthesis. To evaluate the incidence and duration of recovery of post-traumatic and postoperative sensory disturbances, the following tests were carried out: sharp/blunt testing, and the two-point discrimination test as conventional clinical examination methods, and electromyographic recording of the masseter reflex to calibrate the clinical findings. To establish the sensory status of the inferior alveolar and the infraorbital nerves in the region of the fracture, and on the intact and control sides, the tests were performed pre-operatively and postoperatively on the seventh day, after 4 weeks and after 3, 6 and 12 months. The incidence of post-traumatic sensory disturbance was 46% for mandibular fractures and 65% for fractures to the midface (sharp/blunt test, two-point discrimination test). The rate of postoperative sensory disturbance in surgical treatment of mandibular fracture involving the region of the intra bony course of the inferior alveolar nerve, including the post-traumatic sensory disturbance, was 76.9%, and 55% following surgical treatment of midfacial fractures. The incidence of persistent sensory disturbances following surgical treatment was 7.7% in the case of mandibular fractures, and 15% in the case of midfacial fractures (sharp/blunt test, two-point discrimination test, masseter reflex). Recovery of neurological function is delayed in the presence of a displaced fracture (> 1 mm) as compared with non-displaced fractures. For the postoperative calibration of sensory disturbances, electromyographic recording of the masseter reflex from the fourth postoperative week onwards has proved useful.