Measurements of γi (number of electrons per incident ion) for cesium ions on atomically clean tungsten surfaces are reported. Vacuum conditions were such that subsequent to heating the tungsten to 2400°K a monolayer of gas was formed on the surface in ~4 hours. Since measurements were taken within 30 seconds after heating the tungsten to this temperature, the surface contamination is <0.3% of a monolayer. The striking feature of these data is that the yields are smaller than previously reported. It was noted during the experiment that the yield increased if background gases were allowed to accumulate on the tungsten surface.