In this study we report the simulation of the intraseasonal oscillation of the tropical atmosphere (TIO) in the coupled model GIOTTO. The model produces a zonal wave number one eastward propagating disturbance with a mean period of 42 days, which is in good agreement with the observed TIO periodicity. The simulated TIO, however, seems to be influenced by errors in the model mean state. In particular, the errors in the sea surface temperature of the tropical Pacific appear to have a significant impact on the oscillation, affecting its spatial distribution and producing an excess of TIO activity over the eastern Pacific. Despite of these shortcomings, the model seems to be able to reproduce some of the air--sea interaction mechanisms which characterize the observed TIO. ¿ 1999 American Geophysical Union