A semi-empirical model for condensation on horizontal, integral-fin tubes has been adapted to account for ’fin efficiency effects’. Specimen calculations have been made to investigate the effect of tube geometry and material on the enhancement ratio for condensation of steam and CFC11. The best fin spacing was found to be only weakly dependent on the other geometric variables and fin thermal conductivity. The best fin thickness was more strongly dependent on fin thermal conductivity. For the refrigerant the optimum fin thickness was smaller than presently used in practice. The model gave satisfactory agreement with experimental data for CFC113 and steam for typical fin geometries. In the case of CFC113 the enhancement ratio was almost independent of fin thermal conductivity for conductivities exceeding around 50 W m-1 K-1.