In 1998, light trucks accounted for over 48% of new vehicle sales in the U.S. and well over half the new Light Duty vehicle fuel consumption. The Light Truck Clean Diesel (LTCD) program seeks to introduce large numbers of advanced technology diesel engines in light-duty trucks that would improve their fuel economy (mpg) by at least 50% and reduce our nation's dependence on foreign oil. Incorporating diesel engines in this application represents a high-risk technical and economic challenge. To meet the challenge, a government-industry partnership (Department of Energy, diesel engine manufacturers, and the automotive original equipment manufacturers) is applying joint resources to meet specific goals that will provide benefits to the nation. Caterpillar initially teamed with Ford Motor Company on a 5 year program (1997-2002) to develop prototype vehicles that demonstrate a 50% fuel economy improvement over the current 1997 gasoline powered light truck vehicle in this class while complying with EPA's Tier II emissions regulations. The light truck vehicle selected for the demonstration is a 1999 Ford F150 SuperCab. To meet the goals of the program, the 4.6 L V-8 gasoline engine in this vehicle will be replaced by an advanced compression ignition direct injection (CIDI) engine. Key elements of the Caterpillar LTCD program plan to develop the advanced CIDI engine are presented in this paper.