This paper describes the importance of biological nitrogen fixation (BNF) by legumeRhizobium symbiosis to tropical agriculture, the evolution of BNF paradigms, creation of strategic alliances to combat soil fertility degradation, and accomplishments of collaborative BNF-related research at CIAT-TSBFI. It suggests that a holistic-multidisciplinary-systems approach is needed to integrate BNFefficient arid stress adapted legumes into smallholder systems. It proposes a number of research and development priorities for
