Recent summaries of the distribution of the Amazonian manatee Trichechus inunguis record specimens from much of the Central Amazon Basin in Brazil, eastern Peru, and extreme southeastern Colombia, but not Ecuador. During October and November of 1983 we searched for manatees in the Rio Aguarico and Rio Cuyabeno systems of Napo Province, eastern Ecuador. Herein we document the existence of Amazonian manatees in Ecuador, provide rough estimates of their current distribution, describe several aspects of their ecology in Ecuador, document use of manatees by indigenous peoples, and document the current commercial harvest of manatees for meat. Manatees were observed by us at several separate localities in the Amazonian lowlands of eastern Ecuador. Additionally, we report several observations by others as well as a published historical record previously overlooked. Our observations of manatees are from blackwater habitats in undisturbed, primary, lowland rainforest in water with a pH of 5.5 to 6.0 and temperature of 25.0 to 30.7?C. In the upper Cuyabeno region, the Siona Indians, who have harvested manatees for generations, have a self-imposed ban on manatee hunting to protect the few remaining animals in their waters. Settlers, the military, and a commercial meat hunter continue to actively harvest Amazonian manatees in Ecuador and adjacent Peru. Much of the meat obtained is used by either the Ecuadorian or Peruvian military. We found manatees abundant at only one locality, Laguna Lagarto Cocha. However, this population is being actively hunted, and the meat sold to the local military outposts. We estimate that if the current level of harvest continues unabated, Amazonian manatees will be gone from Ecuador within 10-15 years. RESUMENRecientes sumarios de la distribuci6n de los manaties amaz6nicos Trichechus inunguis registran especimenes de la mayor parte de la cuenca amaz6nica en Brasil, el oriente de Peru, y el suroriente de Colombia, pero no de Ecuador. Durante octubre y noviembre de 1983 nosotros fuimos en busca de manaties en los sistemas de los rios Aguarico y Cuyabeno de la Provincia del Napo, Ecuador oriental. Aqui documentamos la existencia de manaties amaz6nicos en Ecuador, proveemos estimaciones aproximadas de su actual distribuci6n, describimos varios aspectos de su ecologia en Ecuador, documentamos el uso de manaties por gentes indigenas, y documentamos la cosecha comercial actual de manaties para carne. Manaties feuron observados por nosotros en varias localidades separadas en las tierras bajas del Ecuador oriental. Adicionalmente, reportamos varias observaciones por otros, asi como tambien registros hist6ricos publicados que fueron previamente pasados por alto. Nuestras observaciones de manaties son de habitaciones en aguas negras en selva iluviosa primaria no alterada de tierras bajas, en aguas con un pH de 5.5 a 6.0 y temperatura de 25.0 a 30.7?C. En la regi6n del alto Cuyabeno, los indios de la tribu Siona, quienes han cosechado manaties por generaciones, se han impuesto asi mismos prohibicion...