Prekindergarten programs, which require a large investment by state, local, and federal agencies, have been growing rapidly in recent decades. This growth has precipitated a great deal of interest in program effectiveness, and much research has been conducted to determine what types of benefits prekindergarten programs bring and how long those benefits can be expected to last. Comprehensive evaluations of prekindergarten programs take into account the costs of the program, the quality of services that the program delivers, and the characteristics of different programs. This entry describes evaluations of prekindergarten programs, including the types of information they provide and common research designs.