A general circulation model of the tropical Pacific Ocean is used to simulate the seasonal cycle in response to two sets of forcing functions. The first set consists of climatological estimates of the stress and heat fluxes, and the second set is derived from an atmospheric general circulation model. In most areas the model fluxes are within the levels of uncertainty in the climatological estimates. Although qualitatively similar, the two flux data sets produce two very different ocean model simulations of near surface conditions. In the expereiment with climatological fluxes the east Pacific cold tongue is too cold whereas the west Pacific temperatures are well simulated; the North Equatorial Counter Current (NECC) is too weak and the strength of the undercurrent agrees well with observed estimates. In the experiment with model fluxes the cold tongue is similated reasonably well but the west Pacific temperatures are too high; the NECC is too strong and the undercurrent is rather weak. These results, and how they relate to the forcing, are discussed in detail. It is concluded that the ocean model simulation is very sensitive to the differences in the surface forcing functions. The ocean model results are compared with those from other simulations of the seasonal cycle in the tropical Pacific. ¿ American Geophysical Union 1990