As part of an effort to shift focus from the emissions performance of pre-production prototypes in certification to the emissions performance of in-use vehicles, the US Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) instituted the “CAP 2000” program. As part of that program, manufacturers are required to retrieve customer-operated in-use vehicles and test their emissions. The EPA and CARB rules contain specific sample size and mileage criteria. The program has been in place for over 15 model years. This paper examines the in-use performance results for 3115 refueling tests, 3844 hot soak+2-day diurnal evaporative emission tests covering five sets of regulatory emission standards, and evaluates several related regulatory issues such as in-use durability and the effectiveness of evaporative on-board diagnostic (OBD) systems.