The results of the simulation of multi-tubular Fischer-Tropsch reactors based on a two-dimensional pseudo- homogeneous model are presented. The model takes into account the intrinsic kinetics of two commercial iron and cobalt catalysts, intraparticle mass transfer limitations, and the radial heat transfer within the fixed bed and to the cooling medium (boiling water). The effective rate with Co is slightly higher than with Fe. Hence, a temperature level can be used for Co that is 20 degrees C lower compared to Fe. The conversion and product selectivies are then almost the same and the reactor can be operated safely without a temperature runaway. The results of the simulations are consistent with literature data and show that there is still room for improvement of fixed bed FT reactors, e.g., by an enhanced heat transfer.