Traditional client-server applications relegate query and persistence operations on their data to database systems. The database system operates on data in the form of rows and tables, while the application operates on data in terms of higher-level programming language constructs (classes, structures etc.). The impedance mismatch in the data manipulation services between the application and the database tier was problematic even in traditional systems. With the advent of service-oriented architectures (SOA), application servers and multi-tier applications, the need for data access and manipulation services that are well-integrated with programming environments and can operate in any tier has increased tremendously. Microsoft‘s ADO.NET Entity Framework is a platform for programming against data that raises the level of abstraction from the relational level to the conceptual (entity) level, and thereby significantly reduces the impedance mismatch for applications and data-centric services. This paper describes the key aspects of the Entity Framework, the overall system architecture, and the underlying technologies. Categories and Subject Descriptors: