Desalination offers an opportunity for source diversification of water for many communities, along with possible defenses against security threats potentially affecting clean water supplies. The economic costs associated with constructing and operating desalination plants in South Texas are investigated. Primary data utilized in the analysis include engineering considerations and actual costs associated with existing and plants under construction in South Texas. Specific costs considered include raw water acquisition and transport, pretreatment, and purification. Sensitivity parameters include source and quality of raw water, energy costs, size of plant, and other heuristic aspects of plant design and development. Annuity equivalent costs are reported on a per ac-ft of finished water basis, f.o.b. desalination plant.