BACKGROUND AND OBJECTIVES: More insight into donor health and behaviour may contribute to more efficient and focused strategies regarding donor care and management. Donor InSight (DIS) is a Dutch cohort study of blood and plasma donors. We aimed to outline the objectives and methods of DIS, describe the cohort, and compare it to the active Dutch donor population. MATERIALS AND METHODS: In 2007-2009 (DIS-I, n = 31 338) and 2012-2013 (DIS-II, 34 826, of whom 22 132 also participated in DIS-I) questionnaire data on demographics, donation, lifestyle, family composition, health and disease were collected. A second follow-up (DIS-III, n = 3046), including donors with differing haemoglobin trajectories, was completed in 2015-2016. DIS-III includes data on genetic determinants, iron and red cell indices. Representativeness of the DIS-I sample for the entire Dutch donor population was assessed by comparing characteristics of both. RESULTS: Donor InSight was initially set up because of a need for more detailed information and evidence as a basis for decision-making in blood banks. DIS-I sample is comparable to the total Dutch donor population in terms of age, body mass index, haemoglobin level, blood pressure, blood type and donation behaviour. CONCLUSION: Donor InSight is a cohort study representative of the Dutch donor population. It provides evidence to support evidence-based decision making.