Agricultural research and development (R&D) has being conducted in the upland districts of Cambodia to develop new farming systems and crop management technologies. Levels of farm income in these areas are relatively low due to small farm sizes and low crop productivity. Work is also planned to encourage the process of adoption of these technologies, and here we investigate how this process can be facilitated. A literature review identifies two important technology characteristics, ‘relative advantage’ and ‘trialability’, for successful adoption. Minimum or target rates of return on investment in new technologies are discussed as a means of investigating how much improvement in relative advantage might be enough to encourage successful adoption of the technology. A number of economic assessments of new crop methodologies in Cambodian upland districts and farming systems are presented. Some technologies show an encouraging return on investment from the viewpoint of the Cambodian farmer – rhizobium inoculation of soybean seed had an indicated return of up to 600% on the investment depending on the cost to the grower. Other issues are also likely to be important in discussing change to farming systems, for instance social issues in the village/community context. We present a proposal for a participatory learning process in which economic and social issues are highlighted, to encourage adoption of new crop technologies in local Cambodian contexts.