Technological change has certainly contributed in a very important way to economic growth in the United States. Although existing studies have not been able to estimate this contribution with great accuracy, they have certainly indicated that this contribution has been large. Moreover, although econometric studies of the relationship between R&D and productivity increase have been subject to many limitations, they provide reasonably persuasive evidence that R&D has an important effect on productivity increase in the industries and time periods that have been studied. Turning to the adequacy of the nation's investment in R&D, there is too little evidence to support a very confident judgment as to whether or not we are underinvesting in certain types of R&D. However, practically all of the studies addressed to this question seem to conclude, with varying degrees of confidence, that we may be underinvesting in particular types of R&D in the civilian sector of the economy, and the estimated marginal rates of return from certain types of civilian R&D seem very high. Additional research is badly needed to determine more adequately the relationship of R&D to economic growth. I have indicated a number of specific areas where work is needed.