Potential government regulations and financial incentives for encouraging pollution reduction retrofits on diesel vehicles are discussed. An integer program is developed to model profit-maximizing fleet owner behavior in the context of potential government programs. The model is intended as a tool both for fleet owners and for government administrators. It allows for mandated retrofits, mandated percent reductions of specified emissions, fixed grants for performing retrofits, and grants per gram of pollution prevented. It treats the fleet size and miles remaining for each vehicle as fixed and known at the time retrofits are made. Retrofits are all assumed to take place in the present, but benefits and costs are distributed over time. A case study is used to demonstrate how a sample fleet owner would respond to various incentives. Potential directions for future research are discussed.