Calculations are presented of the adsorption behavior of Xe films on two different surfaces. One is bulk Cs metal; the other is a graphite surface, covered by a monolayer of Cs. With data obtained from grand canonical Monte Carlo simulations, it is found that a Xe wetting transition occurs on the Cs monolayer within the temperature interval 190 to 200 K. On the Cs metal surface, negligible adsorption occurs over the full temperature range of the simulations, which come close to the critical temperature. Experimental testing of these predictions is proposed.