Past research involving R and D data has produced results which have suggested a number of specific relationships between research and development activities and economic growth, and have helped to identify certain characteristics of the process of technological change. However, many of these results remain ambiguous and their quantitative interpretation and synthesis have been hampered by the absence of definitive data. Many problems surround the concept and measurement of technological change. Until recently, limitations of the R and D data precluded analyses of R and D inputs in the theoretically preferred form of capital stocks. Some of the past research and theoretical discussions are reviewed. An approach is suggested for constructing systematic data which would permit a better focus on technological change than the data now available. 23 references.