A biomarker (biological marker) is a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenetic processes or pharmacological responses to a therapeutic intervention. Expectations are high for the development of biomarkers since they make it possible to achieve a significant improvement in the diagnosis and classification of diseases like Parkinson’s disease. As a surrogate marker for clinical studies, a biomarker can also be used to determine the efficacy of novel therapeutic interventions, such as neuroprotective strategies, and for monitoring the progress of the disease. Imaging techniques (18F-DOPA PET, 123I-β-CIT SPECT, MIBG scintigraphy, functional imaging), clinical tests (e.g. hyposmia, micrography, hyperechogenicity, apomorphine test), biochemical markers (e.g. α-synuclein and neuromelanin antibodies, oxidative and mitochondrial markers) and genetic tests for hereditary forms (PARK1 to PARK11) are evaluated for their suitability.