Exhaust after-treatment is considered an enabler for widespread implication of higher fuel efficient diesel engines. In the last decade extensive research has resulted in the development and advancement of many after-treatment technologies. However there are still many unanswered questions that relate to how these technologies can work together synergistically versus in opposition if intimately integrated with one another. It is anticipated that in the future there will be a need to minimize the volume and mass of after-treatment systems on ever increasingly more complex truck platforms. However, to-date research focused on combining technologies into an integrated system has been relatively sparse. With the inevitable need to consider how SCR and DPF technologies will function in synergy to reduce both NOx and PM, as well as how CO and hydrocarbons (HC) need to be managed, an intergraded investigation and approach is essentially mandatory. The determination of important synergies will require study both under steady-state and through transient conditions.