The Parkinson’s Progression Marker Initiative (PPMI) is an observational, international study designed to establish biomarker defined cohorts and identify clinical, imaging, genetic and biospecimen Parkinson’s disease (PD) progression markers to accelerate disease modifying therapeutic trials. A total of 423 untreated PD, 196 Healthy Control (HC), 64 SWEDD (scans without evidence of dopaminergic deficit) subjects, and 65 Prodromal subjects (individuals with hyposmia or REM Sleep Behavior Disorder) were enrolled. PPMI is actively enrolling affected and unaffected individuals with genetic mutations in LRRK2, GBA, or SNCA through the end of 2018. For the most up to date enrollment numbers, please visit http://www.ppmi-info.org/study-design/study-cohorts/. To enroll PD subjects as early as possible following diagnosis, subjects were eligible with only asymmetric bradykinesia or tremor plus a dopamine transporter (DAT) binding deficit on SPECT imaging. Acquisition of data was standardized as detailed at www.ppmi-info.org.