Linking and integrating data from different data systems can help U.S. states, territories, and other entities answer critical questions about children and families, their needs, and experiences with IDEA services and supports. The 2021 State of the States Survey provides information about how Part C early intervention (EI) programs and Part B 619 early childhood special education (ECSE) programs are linking and integrating program data with each other and with other early childhood, health, and human services data systems. The survey data also address states' plans for additional linking and integration. Data reported in this brief come from survey responses of EI program staff in 55 states, territories, and entities and from ECSE program staff in 51 states, territories, and entities. Key findings include: (1) many states linked or integrated data between their EI and ECSE programs; (2) EI programs in education lead agencies had different data linking and integration capacities and plans than those of EI programs in other lead agencies, such as health; and (3) states that had already linked or integrated their EI and ECSE data were more likely than those with no data linking or integration to have plans for additional linking and/or integration.