Treatment of diesel engine exhaust

A diesel exhaust treatment system for treating exhaust gas from a diesel engine comprises at least one diesel particulate filter, at least one diesel exhaust fluid mixing chamber and at least one selective catalytic reduction converter (SCR). In one desirable embodiment, plural diesel particulate filters are arranged in parallel and plural SCRs are arranged in parallel. These components including the diesel exhaust fluid mixing chamber can be included in a common housing with the exhaust flow reversing directions a plurality of times as it passes through the treatment system from an exhaust inlet to an exhaust outlet. The housing can be coupled to one vehicle frame rail with most of the housing and components contained therein positioned outside the outer surface of the one frame rail.