Parkinson’s disease (PD) is recognized as presenting with a broad spectrum of motor and non-motor symptoms, and varying disease progression. PD has traditionally been categorized based on an individual’s clinical appearance, with the assumption that underlying biological features cluster within each. Alberto Espay, MD, FAAN, University of Cincinnati, Cincinnati, OH, discusses the limitations of subtyping based on clinical characteristics and the importance of defining distinct biologic subtypes. Successful biological subtyping would have important implications, enabling more accurate prognostication and targeted treatment. This interview took place during the 2021 International Congress of Parkinson’s Disease and Movement Disorders.