Improved surface and boundary layer models have been developed and implemented in the Goddard Institute for Space Studies (GISS) general circulation model (GCM). The new boundary layer model retains the methodology of the Model 2 version in which the surface winds are interpolated using a model profile but amends the approximations that were previously used to keep the model analytical for ease of computation. The new surface layer model is entirely different than that previously used in the GISS GCM and uses similarity theory to compute the transport coefficients, drag coefficient, Dalton number, and Stanton number. The combination yields distinct improvements in the general circulation characteristics of the GISS GCM. The new boundary layer and surface models were chosen to allow surface properties to be precomputed, resulting in minimal impact to the overall execution time. This is particularly important in a GCM used for climate experiments with timescales spanning centuries.¿ 1997 American Geophysical Union