The purpose of this study was to investigate the prevalence of nocturnal bruxism, the characteristics of bruxofacets, and the reduction of symptoms in temporomandibular disorder (TMD) patients. The study involved the observation of bruxofacets on a stabilization splint. Twenty-six patients (22 women and 4 men, 16-54 years of age) with signs and symptoms of TMD were given an initial examination before using a splint, and then at intervals of one, three, six and ten weeks after a stabilization splint was first used. In 88% of the patients (n = 23) active shiny facets or scratches caused by nocturnal bruxism appeared on the occlusal surface of splints within ten weeks. In 52% of the 23 patients these facets were created by bilateral mandibular excursions, in 35% by small lateral movements, and in 13% by unilateral excursions. Subjective pain and the Craniomandibular Index in patients had decreased after ten weeks (p < 0.001), but a reduction of symptoms did not differ according to the patterns of the bruxofacets. It was concluded that most TMD patients have a parafunctional habit, namely bruxism. Further research is needed to produce more convincing evidence of a true cause-and-effect relationship between nocturnal bruxism and TMD.