We use the new growth theory framework and panel cointegration techniques to analyse the effect of international agricultural technological spillovers on total factor productivity growth for a sample of 47 countries during the period 1970–1992. The analysis shows that total factor productivity is strongly influenced by domestic as well as foreign public research and development (R&D) spending in the agricultural sector. Geographical factors matter, in that countries located in temperate zones benefit from technological spillovers more than countries located in tropical zones. We find that the rate of return to agricultural R&D spending is higher in tropical countries. This could justify new support and an even greater investment in agricultural R&D for these countries.