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Information on the effect of temperature on B adsorption by soils and soil minerals is scant. These data are needed to understand B availability. Boron adsorption on goethite, gibbsite, kaolinite, montmorillonite, calcite, and two arid zone soils was investigated as a function of solution pH (3-12) and reaction temperature (10, 25, and 40 degrees C) after 2 h of reaction time. Boron adsorption on all materials increased from pH 3 to 7, exhibited a peak at pH 7.5 to 10, and decreased from pH 10.5 to 12. Temperature dependence measured as the increase of the B adsorption maximum at 10 degrees C compared with 40 degrees C on reference minerals increased in the order: calcite (3%) < goethite (7%) < gibbsite (18%) < montmorillonite (-20%) < kaolinite (26%). The kaolinitic soil exhibited greater temperature dependence than the smectitic soil. The B adsorption reaction was exothermic since B adsorption decreased with increasing temperature for all materials, except for montmorillonite at high pH. Highly specific ion adsorption is expected to be exothermic, suggesting an innersphere adsorption mechanism for B on all reference minerals except montmorillonite.