Cassava, maize, rice, groundnuts and plantains constitute the main food crops in Zaire. Rice is a staple food in several regions though its consumption has thus been concentrated in the urban centers. The Department of Agriculture had estimated that rice consumption increased at an annual rate of 2.1 percent for the 1971-74 period and it has also predicted that this rate may reach 9.1 percent by the end of the decade. One of Zaire's key problems is to meet its domestic demand for rice. The government policy of fixing annual hectarage targets for rice and other crops to be achieved through the opening of new land and through exhorting farmers to grow more rice has not succeeded in closing the gap between supply and demand. The focus now is on development programs to increase the commercial production of rice, maize and other major crops. As is the case for most food crops, there is an urgent need for micro-economic research at the farm level to help guide policy makers in increasing rice production. A generalized introduction of fertilizer and high yielding seeds at the small farm level, the adoption of a mechanical technology and the diffusion of irrigated rice system constitute major elements of improved systems of rice farming being presently contemplated in Zaire. In contrast with the agriculture of some West African countries, fertilizer diffusion has not yet reached the vast majority of small holders in various regions of Zaire although they have some use of improved seeds. This paper will first attempt to evaluate the impact of a fertilizer adoption at the small farm level in traditional upland rice farming in the forest zone and later deal with a comparative analysis of an improved upland rice and an irrigated rice farming systems in savannah area where both the objective of increasing rice output and the farmer's revenue are contemplated.