In many countries in Sub-Saharan Africa, rapid urbanization has led to a surge in demand for rice in urban areas. However, most of the supply depends on imported rice since rice is not a staple food in the rural areas and domestic production is still limited. In order for domestically grown rice to compete with imported rice, improvements in the productivity of rice cultivation are essential in Eastern Uganda. Although rice production has been expanding since the end of the 1990s, its productivity is quite low because basic rice cultivation practices have not been widely adopted. To raise this low level of productivity, JICA has provided training on basic production practices along with small irrigation schemes that are constructed by the farmers themselves. This study attempts to understand the impacts of the demonstration of or training in improved lowland rice management practices on their diffusion and on rice yields using the case of the JICA program in Eastern Uganda. The most important finding of this study is that lowland rice yields can be extremely high in Uganda if basic production practices, such as bunding, leveling, and straight-row planting, are adopted along with the introduction of modern rice varieties and the use of simple irrigation systems, even if chemical fertilizer is not applied. The major challenge is how to find the most appropriate means of disseminating such a package of improved production practices to the farmers. According to our analysis, the intensity of participation in the training is the key to the adoption of these basic production practices. It was also found that training participation decreases the further the distance the participants live from the demonstration plot.