Lake Titicaca is the largest freshwater lake in South America and the highest of the world’s large lakes. The Desaguadero River links Lake Titicaca to lakes Urur Uru and Poopo and, in wet years to the Coipasa Salt Marsh. Lake Titicaca is bordered by both Bolivia and Peru. The main international lake management problem for the Lake Titicaca/Desaguadero River/Lake Poopo system involves the use of water resources. The maximum usable flow in the Titicaca basin (only 20–25 m3 s–1), is dramatically less than the estimated demand. Water transfer and irrigation projects will have to be strictly prioritized on the basis of environmental, social, economic and hydrological criteria. Establishing the overall volume and demand for water in the Titicaca system has been critical to making good management decisions. Agreements for the study and management of Lake Titicaca between Peru and Bolivia date back to 1955 when both countries signed a document declaring ‘the indivisible and exclusive joint ownership of both countries of the waters of the lake’. Over time, the two countries agreed to create a Binational Autonomous Authority that would have full autonomy for Titicaca–Desaguadero/Poopo system decisions related to implementing the master plan that they had developed. Although it is hard to quantify conservation success in large lake regions, water use projects are being prioritized, city wastewater pollution in the Bay of Puno is being reduced and ameliorated and a large biodiversity project through the Global Environment Facility is underway.