Objective: This article reports the detailed analysis of antiparkinsonian drug therapy in 78 consecutive Parkinson's disease (PD) patients undergoing deep brain stimulation (DBS) of the subthalamic nucleus (STN). Methods: The amount and type of antiparkinsonian drugs - including l-dopa, dopamine receptor agonists, associated drugs such as catechol-O-methyl transferase and monoamine oxidase inhibitors, amantadine and anticholinergics - were quantified before surgery and at two control visits 1 and 3 years following chronic STN stimulation. Results: The l-dopa mean daily dose was reduced by approximately 60% after 1 year and remained stable after 3 years. Apomorphine, bromocriptine, tolcapone and selegiline were withdrawn after STN-DBS. Three years postoperatively, 9 patients (11.5%) no longer required l-dopa and 6 patients (7.7%) completely stopped all dopaminergic medications. More patients were on monotherapy with either l-dopa or dopamine receptor agonist, and fewer patients required combined treatment of dopamine receptor agonist and l-dopa compared with the pre-surgical condition. Conclusions: Dopaminergic drug treatment is persistently reduced and simplified following chronic STN-DBS for up to 3 years.