The purpose of this report is to develop regional estimates of 12 MOBILE2 input variables for use in the MOBILE2 computer program and its supporting documentation. The 12 variables are: mileage accumulation by age, vehicle registrations by age, average trips/day, vehicle miles, total vehicle miles traveled fractions, fraction of vehicles with air conditioning, air conditioning usage, average temperatures, average humidity levels, average percent vehicle miles traveled in cold/hot starts for catalysts and non-catalysts vehicles, fraction of trips with extra load or trailer towing and speed. The regions discussed in this report are low-altitude non-California, high-altitude non-California and California. Data for California is presented separately from that of other 49 states because the motor vehicle emission standards in the state of California differ from the Federal standards. Therefore, MOBILE2 includes a separate set of emission factor assumptions for California.