Aims: To determine the effect of amyotrophic lateral sclerosis (ALS) on aspects of masticatory function and to assess the relationship between ALS and the prevalence of traumatic mucosal lesions caused by oral self-injury. Methods: A total of 153 ALS patients and 23 control subjects participated in this crosssectional study. Clinical characteristics including site of onset, medication, type of feeding, and use of noninvasive mechanical ventilation were recorded. The Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) protocol and a specific questionnaire to assess aspects of masticatory dysfunction and frequency of self-injury of the oral mucosa were applied to all participants. Maximum mandibular range of motion, maximum bite force, and maximum fingerthumb grip force were determined and tested with Mann Whitney, Kruskal-Wallis, or chi-square tests. P .05 was considered significant. Results: Maximum unassisted and assisted mouth opening, protrusion, left laterotrusion, and fingerthumb grip force were significantly reduced in both spinal- (n = 102) and bulbaronset (n = 40) patients compared to the control group; however, bite force was reduced only in bulbar-onset patients. ALS patients with tube feeding (n = 16) had the greatest reduction in maximum bite force and mandibular opening. There was no relationship between TMD and ALS. Oral self-injury due to biting was more frequent in the ALS group (29.9%) than in the control group (8.7%) and in the bulbar-onset group (55.0%) compared to the spinal- (20.8%) and respiratoryonset (18.2%) groups. Of the ALS patients in the study, 10% sought dental treatment related to the condition. Conclusion: The ALS patients in this study had a reduction in finger-thumb grip force that was twice as great as the reduction in bite force. The maximum range of mandibular movement was also reduced, especially in bulbar-onset patients. ALS patients did not have a higher prevalence of TMD but did have more traumatic mucosal injury than controls. The dentist should be an integral part of the multidisciplinary team to manage ALS patients. Schlagwörter: amyotrophic lateral sclerosis, craniomandibular disorders, mandibular range of motion, occlusal force, self-biting