Pursuant to a legislative requirement, GAO reviewed the National Highway Traffic Safety Administration's (NHTSA) enforcement and administration of the gray market program, focusing on: (1) the extent to which the program ensures that permanent gray market vehicles are brought into full compliance with federal motor vehicle safety standards; (2) whether adequate controls exist for identifying and enforcing requirements for temporary gray market vehicles; and (3) whether safety considerations warrant continuation of the program. GAO found that: (1) the new gray market vehicle program provides NHTSA with more control over permanent imports, but some problems remain; (2) defective gray market vehicles are not being recalled; (3) NHTSA has not established user fees to cover program costs; (4) Canadian gray market vehicles are handled inconsistently; (4) the NHTSA gray market database is inaccurate and incomplete; (5) NHTSA lacks control over temporary imports; (6) NHTSA control over gray market vehicles depends on their identification by the U.S. Customs Service; (7) Customs does not properly identify all gray market vehicles driven into the United States across the Canadian and Mexican borders; (8) although the current gray market vehicle program has improved NHTSA control over a small portion of all gray market vehicles, safety considerations favor continuation of the program; and (9) NHTSA could provide Customs with greater assistance in vehicle identification by modifying its existing regulations.