This interim report describes the results of mass emissions tests of a number of gasoline powered trucks above 6,000-lb GVW during road driving and chassis dynamometer operation. A constant volume sampler was used to obtain samples during operation on a 7.24 mile course in San Antonio and during the entire 20 minute nine-mode FTP. The agreement between the two, in terms of grams of emission per pound of fuel, was used to determine what road emissions would be from a larger, 145 vehicle, fleet that was subjected to similar tests in the laboratory. Consideration of the end use of data was made with preliminary expressions developed for possible use in determining the contribution of gasoline HDV's to air pollution. Data for those of the test fleet used during the laboratory study are included.