The article is an attempt to analyse the impact of tangible capital formation on the process of economic growth in the OECD countries in 1985-2002. The Author makes a reference to theoretical models of economic growth, which allow for quantification of the relationship between the investment ratio and the economic growth rate. Next, results of empirical research conducted so far into the relationships between investment and economic growth are presented. Nevertheless, the analyses show that the relationship between the abovementioned macroeconomic variables is not unequivocal. The following parts of the article present statistical and econometric instruments, which allow to determine the strength and nature of the capital formation impact on economic growth process. The main conclusion from the analyses is the positive and statistically relevant impact of investment on economic growth of OECD economies in the medium and long term.