The linkage among agricultural research, rural extension and farmers is key to promoting innovation and development processes. In general, works addressing problems in this linkage usually do so tangentially or from specific case studies. A systematic literature review of articles written in English, Spanish and Portuguese was conducted with the aim of identifying and organising the problems affecting the research-extension-farmer linkage. The identified problems were classified into central problems, and problems related to the institutional and management environments, the resources and staff, the epistemological-ideological structure organising the relationship, and attitudinal and subjective factors. The detected problems make up a complex causal network and cannot be addressed independently. Moreover, since they implicitly shape the interaction among research, extension and farmers, the problems related to formal and informal institutional structures, to the incentive systems and to the ways of understanding innovation have a strong incidence in the dynamics of the different linkages.