Modifications of starches can led to new products with new desirable properties and applications in several industrial fields as food, textile, paper and others. In this study samples of cassava starch were treated with standard nitric acid 0.1 and 0.2 mol L-1 at 25 and 45 ºC, respectively, by 60 minutes. After washed, dried and maintained in desiccator up to constant mass, the samples were analysed by TG/DTG whose technique allowed observing three main mass losses and the treated starches shown higher stability in the decomposition. When compared with the untreated cassava starch the gelatinization enthalpy (DSC) of the treated starches decreased mainly with the samples treated with acid at 0.2 mol L-1. The increase of acid concentration and temperature show decrease in the relative crystallinity and low alterations in the average diameter of starch granules.