This publication summarizes the main findings and conclusions obtained from several hydrological studies conducted in Latin America, involving the use of hydrochemical and isotope tools. The studies were carried out in eleven aquifers in seven Latin American Member States as part of a Technical Cooperation Project conducted between 2001 and 2005. The main aspects addressed in the isotope studies were related to groundwater origin and dynamics; interconnection between surface waters and groundwaters; groundwater flow patterns; groundwater modelling; and vulnerability to pollution.