Although the soil in the Paraiba Valley generally presents medium to high acidity, the practice of liming is not yet widespread there. One of the reasons for this is the lack of enough lime sources in its vicinity. As a contribution to the study of the liming problem in the Paraiba Valley, six experiments were carried out on various types of soils in the area, comparing two types of slags with limestone as soil correctives. The slags were obtained from the Usina Siderúrgica Nacional, Volta Redonda and from the São Caetano Steel Plant, São Caetano. They were conducted with the tomato and potato crops. Three levels of each type of slag or limestone, plus a complete fertilizer, were compared. Control plots received only the fertilizer. The results from these experiments indicated that the two types of slag compared favorably with limestone as a calcium source. Both can be recommended as a corrective for soil acidity in the Paraiba Valley, provided that they can be supplied in the granulation as required by the regulations.