Long-term monthly mean rainfall and water discharge data from about 50 rain gauge stations and approximately the same number of hydrometric stations in the Amazon drainage basin were systematically analysed. The longest records approached 100 years in length. Comparison with climatic indices derived from the Tropical Pacific (Southern Oscillation Index-SOI) and the Atlantic [sea surface temperature (SST) anomalies] reveals the influence of the El Niño-Southern Oscillation (ENSO) phenomenon on the variability of Amazonian hydrological regimes. This influence, however, may be strengthened by the tropical Atlantic SST. A similar study of several big rivers in Africa shows that the influence of ENSO is weaker in that continent. The hydrological variability of these streams is better explained by South Atlantic surface temperature anomalies. The Atlantic Ocean could act as a relay between the Pacific and the African continents. Copyright © 2009 John Wiley & Sons, Ltd.