GAO's 15 covert tests at a nongeneralizable selection of Head Start grantee centers found vulnerabilities in centers' controls for eligibility screening and detecting potential fraud. Posing as fictitious families, GAO attempted to enroll children at selected Head Start centers in metropolitan areas (e.g., Los Angeles and Boston). For each test, GAO provided incomplete or potentially disqualifying information during the enrollment process, such as pay stubs that exceeded income requirements. (author abstract)