This study analyzes sources of productivity change in petroleum exploration and development in the United States over the last ten years. There have been several major developments in the industry over the last decade that have led to dramatic reductions in the cost of finding and developing oil and natural gas resources. While some of the cost savings are organizational and institutional in nature, the most important changes are in the application of new technologies used to find and produce oil and gas: 3D seismology, horizontal drilling, and deepwater drilling. Not all the innovation is endogenous to the industry; some rests on outside advances (such as advances in high-speed computing that enabled 3D seismology), as well as learning-by-doing. The increased productivity of mature petroleum provinces like the U.S. helps to maintain competition in the world oil market as well as enhance domestic industry returns.