In order to investigate the effects of topography and diabatic heating,especially the wet diabatic processes such as condensation, feedback by cloud of radiation and cumulus convection etc., five kinds of experiments are made for the ‘active’ periods and ‘breaks’ of the monsoon in India by means of the 5-layer primitive-equation model. The topography incorporated approximates the real setting whereas the initial data are taken from the FGGE-3B records.The experiments show that the diabatic heating including the wet processes plays an important role on the structure and intensity of the vertical circulation along about 80°E. For example, when the moisture content is reduced or when the cumulus convection or all the diabatic processes are neglected, both the extent and the intensity of the monsoon vertical cell decrease. Moreover, the effect of mountains during the break differs from that in the active period. During the former, weaker circulation and less precipitation are found over the mountains in central India but the reverse is true for the active monsoon period.