/ The Tucuruí Dam, which blocked the Tocantins River in 1984 in Brazil's eastern Amazonian state of Pará, is a continuing source of controversy. Most benefits of the power go to aluminum smelting companies, where only a tiny amount of employment is generated. Often presented by authorities as a model for hydroelectric development because of the substantial power that it produces, the project's social and environmental impacts are also substantial. Examination of Tucuruí reveals a systematic overestimation of benefits and underestimation of impacts as presented by authorities. Tucuruí offers many as-yet unlearned lessons for hydroelectric development in Amazonia.KEY WORDS: Tucuruí Dam; Amazonia; Hydroelectric dams; Brazil; Reservoirs; Mercuryhttp://link.springer-ny.com/link/service/journals/00267/bibs/24n4p483.html</HEA