Manufacturers of heavy-duty diesel engines for sale in the United States face an unprecedented reduction in emissions in 2007 and in 2010. Compared to today's levels, a 90% reduction in particulate matter (PM) must be achieved by 2007, and a 90% reduction in nitric oxides (NOx) must be achieved by 2010. This paper focuses on the technology solutions possible for engine makers for the interim 2007-2009 timeframe and discusses the additional NOx reduction strategies for a 2010 compliant engine. The possibility of achieving a larger portion of the interim 2007-2009 NOx standard through in-cylinder control methods rather than by NOx exhaust treatment is discussed. High levels of exhaust gas recirculation (EGR) and advanced injection strategies to modify the conventional diesel combustion process are just two processes that can be accommodated in many of today's engine designs. Variable valve actuation (VVA) will help control air management and residual as well as provide exhaust gas temperature control for exhaust treatment synergy. Advanced control strategies will be used to control transient emissions. Diesel particulate filters (DPF) will be used for the primary particulate control as of 2007, notwithstanding additional PM countermeasures that can be obtained from fuel system control. The remaining significant issues of fuel consumption and durability are discussed in light of alternative solutions.