The study was undertaken during 2001-02 to evaluate the past investment on research and extension of maize in Bangladesh. For the purpose, Economic Surplus Model with ex-post analysis was used to estimate the returns to investment on composite varieties and hybrids of maize that have replaced the local varieties. The growth rate of area, production and yield of maize were increased dramatically after the release of maize varieties. The internal rate of return (IRR) to investment was calculated at 23%. During 2000-01, about 65.70% more maize production was made available because of the farmers' adoption of composite varieties and hybrids of maize. The yield of composite varieties of maize ranged from 40 to 65% and hybrids ranged from 73 to 79% higher over the local varieties. Under various assumptions about the research and extension expenditures, the IRR ranged from 17 to 28% and benefit cost ratio from 9 to 19. The accumulated foreign exchange saving since 1992-93 was Tk 291.59 billion. The study indicates that the funding of maize research and extension is a good investment. Therefore, both government and donor agencies should come forward to invest in maize research and strengthen extension activities in the country.