In their 1963 classic Scarcity and Growth Howard Barnett and Chandler Morse argued that resource scarcity did not threaten economic growth. A second investigation in the late 1970s, Scarcity and Growth Reconsidered, reached largely the same conclusion. The 25 years since that work was published have witnessed many developments. The message of Scarcity and Growth that depletion of market resources was not a problem has given way to a concern that "new scarcities" of environmental quality, global climate, and biological diversity are emerging. Resources for the Future recently assembled a distinguished group of international scholars to again address scarcity and growth. This paper describes their charge and summarizes their findings. Technological progress may hold the key to overcoming the scarcity of environmental resources. Market forces may not be enough to motivate the required innovations, which must instead be social and institutional as well as technical and will be constrained by interlinking complexities.