Electrical stimulation of the subthalamic nucleus is an established treatment for patients with advanced Parkinson’s disease with pharmacologically unresponsive fluctuations. Compared with pharmacological treatment, subthalamic neurostimulation significantly improves motor symptoms, particularly during the phases of poor response to drug treatment, and reduces the severity of dyskinesias. Importantly, it also significantly improves quality of life and other integral measures of disease severity. The treatment response can last for more than 10 years, although there is no evidence that levodopa-resistant symptoms are delayed by subthalamic neurostimulation. At present, the mean disease duration for patients at the time of implantation is 12 years. In a recent study (EARLYSTIM) in patients with a disease duration of 7·5 years and fluctuations for 1·5 years, similar improvements in clinical outcomes were reported. These findings suggest that neurostimulation of the subthalamic nucleus could be used earlier in the disease course for carefully selected patients if the benefits of the treatment are weighed against the surgical risks and the lifelong need for specialised care by an experienced team. As mobility is consistently improved during the times with poor mobility by reducing fluctuations and delaying levodopa-sensitive complications, we propose that this treatment changes the disease course.