This paper examines how the efficient use of energy, particularly of oil, can help to create and smooth a transition beyond this one source of energy. It analyzes the dynamics of how the United States used efficiency to improve its oil supply/demand balance throughout the period 1977–1985. The authors explain the unusual events that, in 1986, reversed this steady decline in oil imports. The paper concludes by quantifying the approximate size and cost of the least-cost technical and policy options available to reduce or eliminate oil imports while stretching domestic resources in the years and decades ahead. This paper was originally published as a chapter in The Oil Market in the 1980s: Challenges for a New Era.