This study discusses the effect of easterly wave activities on the strength of the ITCZ. It is hypothesized that precipitating perturbations in the ITCZ is composed of two classes of convective systems. One is randomly distributed in longitude and time, without clear association with the large-scale circulation. The other is closely associated with the large-scale circulation, especially the westward propagating easterly waves. Using satellite remote sensing data (OLR, MSU precipitation, and ERS scatterometer winds), precipitating convective systems associated with the easterly waves are identified and their annual and interannual variability examined. The easterly wave activities and the ITCZ measured by conventional methods, e.g., the mean precipitation and cloudiness, are compared to explore the relationship between the two