To quantify the effects of land cover changes in the Amazon on local and global climate, numerical simulation experiments are conducted using the GISS Global Climate Model II. An ensemble of 6 12-year control runs is generated and compared with a similar ensemble of runs in which the Amazon rainforest is replaced with grassland. The deforestation effect in the Amazon is strong, with reductions in precipitation, evaporation, and cloudiness. We also detect a noticeable impact in several other regions of the world, most of which show a reduction in rainy season precipitation when the Amazon is deforested. This effect is strong compared to that detected when control and deforested runs are combined randomly. The mechanisms for the teleconnection are believed to be related to changes in wind shear and Rossby wave propagation.