With the purpose to examine the behavior of two types of blast furnace slags in the combat against soil acidity, a test was installed comparing them with a dolomitic limestone. This test was established in soil of the Pinda series, at the Experiment Station of the Departamento da Produção Animal, in the Pindamonhangaba county, Paraiba River valley, during a 23-mouths period. Six thousand kilograms per hectare of all the materials studied were utilized and the ploots were kept without cultivation, being cleaned periodically of the natural vegetation. The results obtained showed that the limestone was the most efficient, followed by the two types of scoria with no difference between them revealing themselves also efficient in the control of acidity.