BACKGROUND: Pramipexole is a D3 dopaminergic agonist that has shown a major effect on both sensory and motor manifestations of restless legs syndrome (RLS) in long-term trials. No data regarding the acute effect of low doses of pramipexole have been reported. OBJECTIVE: To evaluate the acute effect of a low dosage of pramipexole (0.125 mg) on sensory symptoms and motor signs of RLS and on the macro- and microstructure of sleep. METHODS: We initially recruited 13 patients affected by severe idiopathic RLS and included 10 of them in our study. For 2 consecutive nights the selected patients were evaluated. Pramipexole 0.125 mg was administered before the second night at 9:00 p.m. A visual analog scale was used to assess the sensory symptoms of RLS. The motor manifestations of RLS and the architecture of sleep were analyzed by polysomnography. RESULTS: After the acute administration of pramipexole, we observed a significant improvement of the sensory symptoms and motor signs of RLS. Several sleep macrostructure and microstructure parameters improved as well. CONCLUSIONS: Our results suggest that low doses of pramipexole are effective in reducing sensory symptoms and motor signs of RLS, even after the first administration.