Malfunctioning emission controls continue to be a major source of emissions from in-use vehicles. We analyze two sources of data on cars with malfunctioning emissions controls: remote sensing surveys and dynamometer tests of cars in the condition they were received. Our analysis indicates that roughly 8 percent of relatively new (2- to 5-year old), modern technology (fuel-injected) cars have malfunctioning emission controls. There is a wide range in the probability of malfunction of specific models, from zero to over 20 percent. Possible causes of high model-specific malfunction probability are poor initial design and/or manufacture.