The heat flow distribution at the Galapagos Spreading Center is compared to results of two-dimensional numerical models for the hydrothermal convection through oceanic crust. The model calculations are based on the equations for fluid flow through porous media adapted for the situation at spreading oceanic ridges. The temperature- and pressure-dependent thermodynamic characteristics of water were used in the fluid flow equations. Models with average permeabilities of approximately 5¿10-15 m2 and penetration depths between 2 and 5 km produce heat flow distributions compatible with the observations at the Galapagos Spreading Center. Because of the convective heat loss, temperatures within the hydrothermal layer are significantly lower than for conductively cooling crust. Two different types of convection cells develop. The one or two cells closest to the ridge axis are fixed in location with respect to the ridge axis. Convection there is characterized by high temperatures (>300 ¿C), rapid flow rates, and low water to rock ratios (~1). These cells remove most of the heat associated with the intrusion process at the ridge axis. Cells farther away from the ridge axis move with the moving plate and serve to prevent the oceanic crust from reheating. Temperatures there typically are moderate to low (<200 ¿C), and flow velocities are lower than those in the axial cell, but water to rock ratios can be very high in these cells.