Potatoes (Solantum tuberosum) were grown on a Lilbourn sandy loam entisol in Charleston, Missouri, with varying rates of potassium fertilizer. Four rates of murate of potash (KCl) were used; 0, 196, 392 and 582 Kg-K/HA. Potassium was measured in tuber and soil by atomic absorption spectrophotometry. The amount of soil potassium was apparently high. Although potassium content in the two cultivars of potatoes, `Norchip' and `Atlantis' was slightly higher (2.3-3.7) as compared to another researcher's data (2%). Obviously, the need for potassium fertilizer for vegetable crops is related to the supplying ability of the soil. Tuber yields (Kg/HA) were higher with added rates of potassium fertilizer than the control, and the results were significant. Yields (Kg/HA) of `Atlantis' were significantly higher than `Norchip.'