In this work we present a theoretical model which allows us to break-down gross investment into investment for expansion, for substitution and for productivity. This more complete breakdown is considered necessary in order to analyse the role which is played by investment in the incorporation of technical change, as well as its impact on the evolution of output and employment. The econometric results offer fresh information with respect to specific technological coefficients lin-ked to investment, as well as to the different stages of growth experien-ced by the Spanish economy between 1964 and 1990.