This paper describes the data obtained when calcium carbonate was added to eleven acid soils from Brazil. One hundred grams of each soil were incubated in Erlenmeyer flask for 60 days with 100 mg and 300 mg of calcium carbonate. After 10, 30 and 60 days, soil samples were taken from each one of the Erlenmeyer flasks and the following determinations were performed: exchangeable aluminum and exchangeable soidity extracted wirh 1 N KCl solution; pH of aqueous soil suspension; pH of the 1 N KCl soil extract. The following conclusions seem justified from the data obtained. a. The addition of calcium carbonate increases both the pH of aqueous suspension and the pH of KCl 1 N extract, depending also upon the amount of CaCO3 applied and upon the soil itself. b. The addition of calcium carbonate decreases both the exchangeable aluminium and the exchangeable acidity content, depending on the applied amount of CaCO3 and on the soil itself. c. The exchangeable aluminium is one of the different components but does not constitute the only source of the soil acidity.