This paper deals with a work carried out in order to study the effect of the neutralization of the soil acidity caused by exchangeable Al³+. Portions of 1.000g of soils were well mixed with increasing amounts of CaCO3, put in vases and incubated for 45 days. The moist soils were kept at 40-50% for their field capacities. The following soils were tested: Sertãozinho and Monte Olimpo series from the county of Piracicaba and 2 and 18 unities from Rio das Pedras county. The treatments were as follows: Treatment Amounts of Ca applied as CaCO3. Control CaCO3 omitted 1 Stoichiometrically amounts related to the exchangeable Al³+ in 1.000g soil 2 Twice as applied in treatment 1 3 Three times the amount applied in the treatment 1. 4 Four times the amount applied in the treatment 1. After the incubation period the soils were dried at the air and ground. Further, the pH and exchangeable Al³+ and H+ were measured. The following conclusions can be drawn: a) The pH of the soils incresead when the amounts of CaC0(3) were incresead. b) In the soil of Monte Olimpo serie, the amount of CaCO3 applied in the treatment 1 was not sufficient to reduce the exchangeable A1+³ to a level non toxic to the plants.