Carbon blacks are the most widely used reinforcing fillers for tires and understanding their role in affecting the rolling resistance of tires is critical in making performance improvements. Without doubt, the upcoming years will see more emphasis placed on the raw materials to reduce the rolling resistance of the tire thereby increasing the gas mileage from the corresponding vehicle. Widening the aggregate size distribution of the carbon black, for example, can make some improvement but this is not the full answer for obtaining the benefits needed by the industry. Numerous other methods for improving this filler’s impact on rolling resistance have been tried and an overview of these approaches will be reviewed. This paper will then focus on the understanding of why carbon black influences tire properties the way it does by examining multiple theories of reinforcement and hysteresis loss in tires. Finally there will be a discussion of the latest improvements for this important raw material to the tire industry.