The Himalayas are an integral part of the Indian monsoon dynamics. In this paper we examine the European Centre for Medium-Range Weather Forecasts 40-year Reanalysis (ERA40) data set in order to quantify the importance of Himalayan rainfall in terms of vorticity generation. We find that Himalayan rainfall is a powerful source of vorticity due to the multiplicative effect of steep vertical gradients in latent heating combined with a large Coriolis parameter. ERA40 shows a maximum in column-integrated and near-surface vorticity generation in the monsoon region over the southern slopes of the Himalayas. We estimate that the total generation of vorticity over the Himalayan region as a whole is at least half that over the Bay of Bengal. Thus Himalayan rainfall is likely to play a central role in amplifying the circulation of the monsoon.