A novel method for the rapid and reliable determination of Cation Exchange Capacity (CIC) of acid and neutral soils is presented. The exchange process is based on the proton, H⁺ ability to exchange cations effectively. The method consists in shaking a 1:10 soil:solution suspension ratio for 10 minutes with HCl (0.1M), then base-titrating the filtrate remaining acidity, from which the CIC-values are computed. Optimization studies were carried out varying 1) soil:volume ratios (1:2.5 to 1:20), using 1 to 10g of soil material; 2) Acid concentration (0.05-0.5M); and 3) shaking time (5-30 min). Seventeen soil materials were analyzed, 13 from WEPAL (Wageningen Evaluating Programmes for Analytical Laboratories) belonging to different countries, and 4 Mexican soils from the national ISP-exchange programme (Programa de Calidad e Intercoparacion de Analisis de Suelos y Plantas). Soils varied in pH-water from 5.11 to 7.00, and 1M-NH₄-Acetate- and BaCl₂-CIC-values from 3-38 cmol(+) kg^-1-soil. Best results were found for the lower shaking times, due to the increase chance of dissolution processes obtained under extended acid contact, especially for shaking times greater than 20 minutes. Although no significant effect was noticed for the different soil:volume ratios studied the amount of soil material used was critical in the manipulation of the filtrates which tilted the optimization of method toward the use of more than 2.5g soil and soil:volume ratios of 1:10 or greater. Regarding the acidity studies, whereas HCl concentrations lower than 0.1M were not sufficient to extract efficiently all exchangeable cations, greater H⁺-levels overestimated the computed CIC-values due to the enhanced dissolution power of HCl concentrations greater than 0.3M. However the more soil material was used the precision of results increased. Best results were obtained when the procedure is based on shaking times between 10 to 20 minutes, HCl-concentration from 0.1M to 0.25M, soil:volume ratios from 1:5 to 1:20, weighting out 2.5g to 10g depending on the amount of soil available. More studies will be carried out to quantify and specify composition and magnitude of exchangeable bases and acids and to adequate the method for calcareous soil materials. Table below shows the relevant data discussed above.