General circulation mechanisms instrumental in both annual cycle and interannual variability of rainfall are studied with reference to key regions of the tropical Americas and Africa, including the Central American–Caribbean area, northern Northeast Brazil, Subsaharan Africa, the Angola coast and the zaïre (Congo) and Amazon basins. For most of these regions, rainfall anomalies tend to be associated with departures in the large-scale atmospheric and oceanic fields that correspond to the pattern changes in the annual alternation of dry and rainy seasons. The interannual variability of climate and circulation thus appears largely as enhancement and reduction of the annual cycle.