Present work was designed about the assignation of thermodynamic acid dissociation constants (pKa) of pravastatin, atorvastatin, and rosuvastatin by using RPLC method. In the experiment, methanol-water binary mixture was chosen as hydroorganic solvent mixture. Chromatographic study was performed with Nucleosil 300-5C(4) column (5 mu m, 250 mm 4.6 mm) and the flow rate of the experiment was adjusted at 1 mL/min. The thermodynamic acid dissociation constant values and the intrinsic retention factors were estimated by use of a non-linear least squares fit of the data. The realibility of the RPLC methodology was investigated statistically using the difference between the experimental and theoretical results. Aqueous pK(a) values were also estimated with extrapolation by means of the Yasuda-Shedlovsky and mole fraction equations. Availability of present procedure in order to quantitatively determine the studied compounds was verified by the validation in suitability with the requirements laid down via ICH (International Conference on Harmonization) guidelines. Implementation of this method was correctly applied to the determination of studied drugs in active pharmaceutical content and in pharmaceutical formulations, with great recovery, well precision and accuracy.