The more than 3000 km continental border between Mexico and the United States is home for more than 11.8 million people. This region has experienced consistent growth since WWII, in some instances doubling its urban area every twenty years. The rapid expansion of urban areas has boomed since the signing of the North American Free Trade Agreement, increasing the settlement of the industry and residential zones and surpassing the planning capacities of the border cities, especially on the Mexican side of the border. Since 1993 institutions like the Border Environmental Cooperation Commission (BECC), have addressed the asymmetries in basic sanitation between the two countries which was a source of contamination for shared water bodies used as potable water. Two groups of investments certified by BECC along the border (Valle de Juarez and Baja California) were analyzed by ad-hoc Results Measurement Methodology to determine how the $253.61 million of US Dollars invested in basic sanitation infrastructure impacted eight communities on the Mexican side of the border. The impact assessment complemented the administrative project close out process, which measured the extent to which the physical targets (bricks and morter) of the certified projects were implemented. The impact Assessment process consists of a determining the impact achieved for the residents based on the use of the infrastructure. It develops a framework to document the results in the chain of inputs, outputs, outcomes and impacts. Evaluation of the results was conducted using four indicators: (1) increase in wastewater residential connections system; (2) overall reduction on the number of latrines and cesspools; (3) reduction in untreated wastewater flowing into international water bodies; (4) reduction in associated diseases and/or exposure to raw sewage and 5) increased quality of life. Data sources included official sources (INEGI and COFEPRIS ), utility data, and surveys. However, the use of tools such as Geographic Information Systems allowed layering of all available data by layers in the case of the four Baja California communities. Surveys complimented official data and focused on specific project area impacts. In the case of Valle de Juarez, testing of water added information on the potential exposures to pathogens and other agents (Giardia and Cryptosporidium). Results indicate that the BECC mandate of improving human health and the environment had been fulfilled. Additionally, projects met fundamental environmental objective of providing access to service, and residents utilized infrastructure and benefitted with improved quality of life. Although several lessons learned are discussed, the Results Measurement Framework proved to be a useful tool. Discussion is presented on how cooperation among US and Mexican agencies were successful in producing the financial and technical resources needed for small and sometimes marginalized communities, to acquire levels of sanitation above the national average.