The program involved conducting twice-weekly I/M (Inspection and Maintenance) emission short tests on twenty-five late model gasoline-fueled vehicles over a 15-week time period. All of the twenty-five vehicles (1981 model year or later) were tested once in the morning and again later that same day following a soak period of at least three hours. The vehicles tested in the program were owned by Southwest Research Institute employees and were selected to represent a variety of vehicle types, emission controls, etc. Emission tests were conducted using two Bear Automotive Type 42-925 4-Gas Infrared Analyzers with generic software. Each emission test sequence included a 'Test Analyzer Specifications' ('TAS') sequence (i.e., 2500 rpm/idle test with emissions measured in both modes), a vehicle conditioning step utilizing three minutes of engine operation at 2500 + or - 300 rpm with the vehicle transmission in neutral, idling in neutral for 15 seconds, and finally a second TAS sequence. The tests were conducted to provide EPA with information regarding variability in short test emission results, impact of off-idle no-load preconditioning cycles on short test emissions, and emission differences between a fully-warmed vehicle and a 'soaked' vehicle having undergone minimum operation. Hydrocarbon and carbon monoxide emissions are reported for each vehicle in tabular and graphical form. Hydrocarbons are reported in ppm and carbon monoxide in percent.