We use the panel data approach with fixed effects to differentiate the long-run rate from short-run level effects of stock market development on economic growth against a sample of 70 countries over the period 1975-1992. The empirical evidence indicates that development of stock markets has significant positive effects on both the long-run growth rate and short-run level of real GDP per capita. Furthermore, we find that the influence of stock markets is mainly through the channel of productivity improvement, rather than capital formation, Physical capital per se only enhances the short-run level of economic development, but has no effect on the long-run growth rate. Finally, the results suggest that stock markets have a stronger impact on growth rate for low-income countries. The conclusions appear to be independent of bias associated with omitted variables and simultaneity between stock markets and economic growth.