Catalytic emission control systems are installed on nearly all automobiles and heavy-duty trucks produced today to reduce exhaust emissions for the vehicles to meet government regulations. Current systems can achieve very high efficiencies in reducing tailpipe emissions once the catalytic components reach their operating temperatures. They are, however, relatively ineffective at temperatures below their operating temperature windows, especially during the cold start period of the vehicles. With the increasingly stringent government regulations, reducing the emissions during the cold start period before the catalytic components reach their operating temperatures is becoming a major challenge.For cold start HC control, HC traps based on zeolites have been investigated and commercialized for certain applications. For cold start NOx control, especially in lean burn engine exhaust, NOx storage and release catalysts have been evaluated. In this paper we will introduce a novel catalyst which we refer to as Cold Start Concept (CSC™) catalyst technology. This cold start catalyst not only stores HC and NOx at low temperatures with very high storage efficiencies, but also converts a significant portion of the stored HC/NOx during the warm-up period before the rest of the HC/NOx is thermally released from the catalyst. The HC/NOx release temperature in a cold start catalyst is high enough that the released HC/NOx can be further converted by the downstream catalytic components. In addition, the cold start catalyst also exhibits excellent CO, HC, and NO oxidation activity under normal lean conditions. Both laboratory and engine evaluation results of this new concept will be presented.