Driven in part by concerns regarding global warming, there is a clear trend toward increased sales of light duty diesel vehicles in many parts of the world. This trend can result in many positive environmental benefits including low fuel consumption, and therefore low levels of CO2, low levels of gaseous exhaust CO and HC (especially during cold start conditions), and very low levels of evap orative hydrocarbons. However, increased diesel sales have a downside, relatively high NOx and particulate emissions. These pollutants continue to receive high priority attention in most areas of the world. As a result, countries around the world are increasingly tightening diesel regulations with the result that technology for reducing emissions continues to advance. The variety of regulatory approaches being pursued to reduce diesel NOX and particulate by countries around the world will be reviewed and summarized.