This work was carried out in order to study boron adsorption by samples of three Hapludox, one Acrudox and one Hapludult, all representative soils from the State of São Paulo, Brazil. Simple linear correlation and more complex relationships, trough the stepwise regression program, were obtained between both soluble boron extracted with hot-CaCh 0,0l mol/L (HCB) solution and adsorbed boron, and chemical atributtes (the usual components of routine soil fertility analysis, and the contents of total, free and amorphous iron and aluminum oxides), the usualy physical attributes of the soils (sand, silt and clay content) and the specific surface. Toe effect of correcting the soil acidity, with calcium carbonate, on the adsorption of boron was also quantified. Finally, the Langmuir and Freundlich isotherms were employed to study the boron adsorption. Hot-CaCh solution extractactable boron was highly correlated with sand and clay contents and with specific surface area. Correlations with chemical attributes were not as high, being statistically significant only for CEC and total aluminum oxide in ali the five soils and for organic carbon in the four Oxisols. Multiple regression analysis showed that total aluminum oxide and exchangeable calcium and aluminum were correlated with HCB, explaining 85% of its variation. xi Calcium carbonate promoted an increase in the amount of adsorbed boron in all soils, but the most outstandLn.g effect was observed in the coarser textured Oxisols. Toe highest correlation coefficients between the adsorbed boron and chemical attributtes appeared with the content of total and amorphous aluminum oxide. High coefficients were also found with sand and clay contents and specific surface. ln the multiple regression, clay content, free aluminum oxide and HCB could explain 93% ofthe variance in adsorbed boron. Both Langmuir and Freundlich isotherms fitted well to the adsorbed data, but Freundlich model exhibited lower sum of deviation. Highest deviations between the values obtained in laboratory and those predicted by both models occured in the clayey textured Oxisols. Highest values for maximum adsorption predicted by the Langmuir isotherm were found in these soils, which were significantly correlated with contents of total, free and amorphous iron and aluminum oxides, as well with the physical attributes. Ninety four percent of the variation in the maximum adsorption could be related to the free iron content. In the other side, total, free and amorphous aluminum oxide content, in a multiple regression equation, could explain 95% of variance of maximum buffer capacity, determined by the product of the K and b constants of Langmuir equation.