Climate change will have significant impacts on agriculture, particularly in East Africa where there is such variation in topography and climate. Modelling studies can help to show where these impacts may be largest, to help guide adaptations to ensure food security in the coming decades. Results suggest that crop yield reductions may be expected over 50% to 70% of the area simulated. At the same time, highland areas in parts of the region may see increases in yield potential, which could have a positive impact on householders'incomes and food security in these places.