A penetração de luz nas águas de rios amazônicosThe paper presents the results of measurements of penetration and reflection of light of 5 different wavelenghts in the waters of 7 localities of Central Amazonia around Manaus: White water of Rio Solimões; decanted white water of a floodplain lagoon "Lago Castanho" of Rio Solimões; black water of Rio Negro; black water of Rio Cuieiras, affluente of Rio Negro. No clearwater river could be examined. Smallest penetration but greatest reflection occurred in turbid Solimões water. In Lago Castanho, penetration increased with distance from Solimões, i.e. with increase of decantation. Greatest penetrations and smallest reflections were found in the black waters of Rio Cuieiras and Rio Negro while the most decanted water of Lago Castanho was between these values. In the black waters, the greater penetration of light of greater wavelenght was more pronounced than in white and decanted white waters. The biological significances of the results are being discussed.