The solubility of commercial grades of five different limestones in 1 per cent acetic acid solution was studied. A pure sample of CaCO3 was included in the tests for comparison. Solubility was measured by shaking 250, 500, 1,250, and 2,500 mg of each limestone material with 250 ml of 1 per cent acetic acid solution for 30 minutes. The chemical composition of the limestones tested and the results on solutility, expressed as CaCO3 equivalent, are shown in table 1. These results are also represented in figure 1. Chemical composition, fineness of grinding, and texture are of importance in the characterization of limestone materials. The solubility in 1 per cent acetic acid solution varies according to those characteristics. High calcium limestones were more soluble than dolomitic ones. The texture influenced the solubility of the dolomitic limestones. Among the dolomitic limestones those of sedimentary origin were the most soluble. According to the particle size of the limestones studied, the nature of these was more important on solubility than fineness of grinding. The relation 1,250 mg of material to 250 ml of solution is recomended for determining solubility of limestones because it gave good results in the differentiation of these materials.