The purpose of this study was to evaluate the influences from variables of preparation on dry residue and total tannins from macerates of Astronium urundeuva barks. Thus, a 3 ² factorial design was used to study the importance of plant proportion (10, 15 and 20 %, w/v) and the ethanol concentration (40, 60 and 80 %, v/v) on the selected response. Mathematical models were fitted according to experimental data. The validated equations were used to generate response surfaces. The analysis of the surfaces showed that the optimum conditions to obtain extractive preparations with high extractive efficiency for tannins were: 10 % (w/v) of plant with ethanol 40 % (v/v) as solvent.