This study examined (1) the relationships between electromyographic-measured nocturnal bruxism, self-reported stress, and several personality variables, and (2) the relationship between belief in a stress-bruxism relationship and self reported stress. One hundred adult bruxers completed a batteryof personality questionnaires, indicated whether they believed in a stress-bruxism relationship, presented for a dental examination, and had dental impressions taken. Subsequentlyu, electromyographic measurements of bruxing frequency and duration were recorded for fifteen consecutive nights. Prior to each night's measurements, subjects indicated their levels of stress for the immediately preceding 24 hours. No overall relationship was established between electromyographic measures and the personality variables nor between electromyographic measures and self-reported stress. Correlations between electromyographic measures and self-reported stress were statistically significant for eight individual subjects. Further, subjects with high levels of stress reported more anxiety, irritability, and depression, and less denial. Subjects who believed in a stress-bruxism relationship reported greater stress.