Food security is a major concern in the east and southern Africa region. While the food crisis has receded somewhat at the international level, within the region urban food prices remain relatively high. Among the food crops, maize is the main staple and legumes an important dietary protein source for the rural poor. Legumes are widely used as an intercrop in maize systems, and are also significant source of income for women. Seasonal variability causes wide swings in food crop yields, including maize and legumes. Rain-fed maize-legume cropping systems show considerable promise in boosting productivity and helping reverse the decline in soil fertility that is a fundamental cause of low smallholder productivity in the region. During July –December 2009 consultations between ACIAR and stakeholders in the region and Australia led to the formulation of the Sustainable Intensification of maize-legume based Farming Systems for Food Security in Eastern and Southern Africa-SIMLESA program proposal and its approval in March 2010. ACIAR is supporting the A$20 million program for 2010-2013 period which is being managed by the International Maize and Wheat Improvement Centre. The program is implemented by NARS in Ethiopia, Kenya, Tanzania, Malawi and Mozambique in collaboration with many partners. The program aims at increasing farm-level food security and productivity, in the context of climate risk and change, through the development of more resilient, profitable and sustainable farming systems.