e mean interannual discharge of the River Amazon in the Atlantic Ocean has been estimated using two methods, independent but complementary After having de ned, in the most logical way, the eastern limit of the Amazon basin, the v\ater balance from Óbidos was established for the 1972-2003 period, e mean interannual discharge at the mouth wouldbe 205,000 m3s-1. A second method was based on ten sets of ow measurements done at the mouth from 1997 to 2008, which correlated very well with the corresponding discharge values observed in Óbidos, is method indicates an interannual ow at the mouth of 208,000 m3 s-1, including 6,000 m3 s -1 that represent the derivation from the Amazon River towards Rio Pará (and the Ocean) by the furos, channels that run in the River Amazon's old arm, With an uncertainty of ± 6%, the interannual contributions of the River Amazon to the Ocean, over the 1972-2003 period, would be 206,000 m3 s-1, and would represent 17% of the total volume of fresh water entering the oceans worldwide.