The electrochemical behavior of valproic acid (VAL) was investigated using square wave voltammetry, cyclic voltammetry, and sampled direct current polarography and a new square wave voltammetric method was developed for determination of VAL in pharmaceutical preparations. VAL showed two reduction peaks at about -0.2 V and -0.8 V vs. Ag/AgCl 3 M KCl with a hanging mercury drop electrode in 0.05 M pH 3.3 Britton-Robinson (BR) buffer. These peaks were named peak I and peak II, respectively. The types of limiting current of both peaks were determined as diffusion controlled based on cyclic voltammetry studies. A linear calibration graph was obtained in the range 1.46 x 10(-4)-1.0 x 10(-3) M. The limit of detection (LOD) and limit of quantification (LOQ) were 1.09 x 10(-4) M (21.05 mu g/mL) and 1.10 x 10(-4) M (144.20 mu g/mL), respectively. Recovery studies for the accuracy of the method were performed by adding known amounts of VAL and it was found to be 109.67 +/- 4.85%. The proposed method was successfully applied to pharmaceutical products on the market.