The Arizona-Sonora region along the U.S.-Mexico border has been called the "front line of ongoing climate change" (Harrison 2009). Due to its rapid growth, industrialization, and climate characteristics, it is recognized as a highly vulnerable region in terms of socioeconomic and climate characteristics. Ensuring future water supply is the region’s highest priority challenge. Climate change projections for reduced precipitation and severe drought. From 2008 to 2011, a binational team of multi-disciplinary researchers led by the University of Arizona and El Colegio de Sonora worked closely with decision-makers, water managers, and disaster relief planners (i.e., stakeholders) to conduct urban water vulnerability assessments of the four urban climate change “hotspots” in the Arizona-Sonora region. These assessments focus on the nexus of climate and water variables, with a 5 to 20 year horizon. Project outputs to date include: 1) four linked urban water vulnerability studies (Tucson, AZ; Nogales, AZ., and Nogales, Sonora; Hermosillo and Puerto Peñasco, Sonora) that identify major regional climate-related vulnerabilities and institutional capacity in the water sector; 2) a Binational Climate Summary for Arizona-Sonora region, in English and Spanish; 3) a series of five stakeholder-scientist workshops; and 4) a new Working Paper series on water, vulnerability, and climate in U.S.-Mexico border region.