Abstract: An internal combustion engine system having a non-catalyzed particulate filter receiving products of combustion at a temperature of frequently above 600° C. and an excess of oxygen of between 0.5 and 0.8% from a stoichiometric diesel engine. A NOx reduction catalyst is positioned downstream of the particulate filter. The engine system may include a turbocharger and the particulate filter and NOx reduction catalyst may be positioned either upstream of the turbine or downstream of the turbine or alternatively the particulate filter upstream of the turbine and the NOx reduction catalyst downstream of the turbine.