In a single-blind, placebo-controlled crossover trial, the acute efficacy of the dopamine agonist pramipexole was investigated in 11 restless legs syndrome (RLS) patients by sleep laboratory methods, with a clinical follow-up for 4 weeks. In 3 nights (pre-treatment, placebo and drug night), objective sleep quality was determined by polysomnography (PSG), subjective sleep and awakening quality by rating scales, objective awakening quality by psychometry. Clinical follow-up consisted of completion of the International RLS Study Group (IRLSSG) Scale, Zung Depression (SDS) and Anxiety (SAS) Scale, Quality of Life Index, Pittsburgh Sleep Quality Index and Epworth Sleepiness Scale. Concerning acute effects, an omnibus significance test for PSG variables demonstrated a global difference between placebo and pramipexole, but none between pre-treatment and placebo. Pramipexole 0.27 mg significantly decreased the target variable periodic leg movements (PLM)/h of sleep as well as all other RLS/PLM variables and improved objective sleep efficiency and subjective sleep quality as compared with placebo. In sleep architecture, sleep stages S1 and S2 and stage shifts increased, while slow-wave sleep and SREM decreased. After 4 weeks of therapy, the total scores of the IRLSSG questionnaire, sleep quality and daytime sleepiness, depression and quality of life also improved. Thus, acute pramipexole markedly reduced PLM measures and slightly improved objective and subjective sleep quality. Follow-up ratings showed a moderate improvement of RLS and sleep quality, and to a lesser extent of daytime sleepiness, depression and quality of life. The psychopathological findings as well as acute sleep architecture changes are reminiscent of those seen after activating antidepressants.