BACKGROUND Sleep bruxism (SB) is characterized by repetitive and coordinated mandible movements and non-functional teeth contacts during sleep time. Although the etiology of SB is controversial, the literature converges on its multifactorial origin. Occlusal factors, smoking, alcoholism, drug usage, stress, and anxiety have been described as SB trigger factors. Recent studies on this topic discussed the role of neurotransmitters on the development of SB. OBJECTIVE Thus, the purpose of this study was to detect and quantify the urinary levels of catecholamines, specifically of adrenaline, noradrenaline and dopamine, in subjects with SB and in control individuals. METHODS Urine from individuals with SB (n = 20) and without SB (n = 20) was subjected to liquid chromatography. The catecholamine data were compared by Mann-Whitney's test (p </= 0.05). RESULTS Our analysis showed higher levels of catecholamines in subjects with SB (adrenaline = 111.4 microg/24 h; noradrenaline = 261,5 microg/24 h; dopamine = 479.5 microg/24 h) than in control subjects (adrenaline = 35,0 microg/24 h; noradrenaline = 148,7 microg/24 h; dopamine = 201,7 microg/24 h). Statistical differences were found for the three catecholamines tested. CONCLUSIONS It was concluded that individuals with SB have higher levels of urinary catecholamines.