The early diagnosis of Parkinson's disease (idiopathic parkinsonism) is important for two reasons. Some never drugs possibly have a neuroprotective effect, which can be utilized maximally only with early onset of treatment. Moreover, diagnostic mistakes may occur early in the course of the disease. Although the hallmark of Parkinson's disease is a syndrome of movement disorders, slight cognitive deficits, depression, or pain with or without paresthesias can be present at an early stage. Therefore, symptoms at the time of the first diagnosis and at the beginning of the first clinical manifestation of Parkinson's disease are often not identical. The diagnosis can be made only clinically, since no biological marker is available up to now. However, in unclear cases pharmacological tests constitute a valuable extension of the clinical examination.