There is still uncertainty when to start medical treatment in Parkinson disease (PD). Lack of availability of an unambiguous neuroprotective treatment and concern of potential short or long term adverse effects of medication often lead to an "wait and see" policy regarding initiation of medical treatment. This can result in insufficient symptom control and potentially reduced quality of life. There is increasing evidence of negative influence on disease progression by delayed onset of medical drug treatment in PD. It is under discussion whether symptomatic treatment in PD supports compensatory mechanisms of the cortico-basalganglionar system which might have been responsible for a physically intact motor function despite considerable and increasing nigro-striatal dopaminergic deficit during the preclinical phase of the disease. Therefore, symptomatic treatment might modify disease progression by supporting compensatory mechanisms within the basal ganglia. In this paper we discuss pro and contra of early medical treatment onset in PD under consideration of hitherto available scientific investigations.