The putative role of the dopaminergic system in sleep bruxism (SB) was studied in a double-blind clinical trial by using low doses of short-term L-dopa in combination with benserazide. We recorded 10 patients with SB in our sleep laboratory for 3 consecutive nights. The first night was for habituation to the laboratory environment. During the second and the third nights, the patients received two doses of either L-dopa or a placebo in a crossover fashion: the first dose 1 h before bedtime and the second, 4 h after the first one. The order of administration was reversed in half the patients. The efficacy of L-dopa was analyzed by using multilevel models. L-Dopa resulted in a significant decrease in the average number of bruxism episodes per hour of sleep, as well as in a significant reduction in the average value of the root-mean-square (RMS) electromyography (EMG) level per bruxism burst. This indicates that L-dopa exerts an attenuating effect on SB. In addition, L-dopa caused a reduction in the variance in RMS values, which suggests that L-dopa normalizes the EMG activity patterns associated with SB.