The mean field equations, which contain no explicit Prandtl number dependence, are shown to provide reasonably accurate predictions of average heat transport for Rayleigh numbers from 2000 to 18000 over a wide range of Prandtl numbers, provided physically observed wavenumbers are used in the calculations. It is concluded from this that the physical significance of Prandtl number in Be´nard convection is principally in setting the ’’preferred’’ wavenumber, i.e., the size of the convection cell.