An ocean general circulation model is used to simulate the thermohaline circulation in the Mediterranean sea during the last glacial maximum and the Holocene, when the sapropel S1 was deposited. The model is forced by prescribed surface temperatures and salinities, where present-day values lead to very realistic surface buoyancy fluxes. Different paleoreconstructions for the surface salinity and temperature distributions during these periods are tested. In both periods, under all reconstructions, antiestuarine flow is maintained at Gibraltar and Sicily. The Holocene circulation has fresh intermediate water produced in the Adriatic and an upward salt flux from the old waters below help maintain its outflow at Sicily. The depth of ventilation around the basin is broadly consistent with the shallowest sapropel layers observed. Shoaling of the eastern pycnocline occurs in all experiments in both periods, possibly indicating enhanced productivity, although the reasons for this are different in each case. ¿ 1998 American Geophysical Union