Cesium-137 (137Cs) soil-to-plant transfer factors obtained in an accidentally contaminated Oxisol in Goiânia and another Oxisol experimentally contaminated show that these soils present higher transfer of 137Cs from soil to plants than previously observed in temperate climates. These differences were discussed in the light of the pedology and geochemical partitioning. Some tropical soil characteristics, such as acidity, low availability of nutritive elements and low content of 2:1 clay type may account for the high mobility for 137Cs even after a long period after contamination. Results of sequential extraction showed that most of the 137Cs is bound to soil oxides.