Symptoms and signs of craniomandibular dysfunction and neurosensory disturbances were studied in 49 patients, who underwent mandibular sagittal split osteotomy with rigid internal fixation. Recordings were made before and at 7 months as well as at 13 months (advancement group, n= 25) or 14 months (setback group, n = 24) postsurgically. Symptoms of craniomandibular dysfunction were valuated by questionnaire. Physical conditions of the mandible were valuated and measured clinically. The neurosensory function of the lower lip and chin was evaluated with a subject history and with sensory tests. The two surgical procedures did not increase the prevalence of symptoms or signs of craniomandibular dysfunction, now was there any major impairment of the neurosensory function as revealed by the tests. Half of the patients of both groups had mild subjective symptoms of disturbance in the lower lip or chin 1 year postsurgically. In the advancement group, the movement capacity of the mandible was mildly reduced 1 year after the operation. In the setback group, initially large retruded contact and intercuspal discrepancies were eliminated by the operation. In the advancement group, on the other hand, the operation resulted in unacceptably large retruded contact and intercuspal distances in 20% of the patients.