This paper analyses how IPRs influence economic growth by use of 39 countries' panel data from 1981 to 2007. The econometric methods include pooled Ordinary Least Squares (OLS) analysis, rolling–windows and recursive analysis and Arellano–Bond dynamic panel data regression. The study findings are as follows: R&D plays a positive impact upon economic development, especially after 1986. Furthermore IPRs play significant role for economic growth. Without proper IPRs, the function of R&D cannot be played efficiently. IPRs tend to play more significant role upon economic growth in 9 Newly–rising Industrial Countries than that in 30 OECD developed countries. IPRs of 9 developing countries are converging with that of 30 OECD developed countries.