The inability to distinguish effective treatments from ineffective ones is a complex problem. One major issue is that the biology of the disease is not well understood— the syndrome known as Parkinson's disease may actually be a cluster of disorders with similar symptoms but different causes. This makes it difficult to use biological measures, also known as biomarkers, to measure whether or not a treatment is effective. It also makes it difficult to diagnose patients at the very earliest stages of the disease, so defining a patient population that would be most appropriate for testing a disease-modifying treatment may not be easy. A second key challenge is how symptoms and functions in people with Parkinson's are measured. There are several well-known clinical assessments for the disease, but they have critical limitations in people with early Parkinson's, mostly because early changes in symptoms or function may not be big enough to be detected by these assessments. Many organizations are working together to address these challenges. A newly-released RAND report, Clinical Outcome Assessments and Digital Health Technologies Supporting Clinical Trial Endpoints in Early Parkinson's Disease: Roundtable Proceedings and Roadmap for Research, summarizes an event held last fall to discuss these issues and how the field can work together to address them, especially through harmonizing methods, sharing data, and synthesizing work that has already been done to build consensus and alignment on patient experiences in early Parkinson's. This gathering also underscored the need for new clinical outcome assessments for early Parkinson's. One novel approach incorporates the perspectives and observations of the family or close friends of people with Parkinson's disease. Many of the earliest changes in people with Parkinson's, such as voice changes, facial masking, and other movements may be most noticeable to people other than the patient. Outcomes reported by such “knowledgeable informants” could be appropriately sensitive to changes in patients in the early stages of the disease. Participants at the gathering also emphasized how important it is for new clinical outcome assessments to obtain and incorporate input from a diverse groups of people affected by Parkinson's.