The electrochemical investigations on 5-methyl-4-(4|-substitute phenylhydrazono)- 2-(5-thioxo-4,5-dihydro-[1,3,4] oxadiazole-2-ylmethyl)-2,4-dihydro-pyrazol-3-ones having substitutions namely -H, -CH3 , -OCH3 , -OC2H5, -Cl, -Br were carried out in Briton-Robinson buffer solutions. Investigations were carried to study the effect of pH, height of mercury column, effect of substituents based on which reduction mechanism was proposed in acid as well as in basic medium. The compounds under investigation exhibit a well defined single wave in the buffer solutions of pH 1.1-7.1 and two waves in solutions of pH 8.1-10.1 in polarographic studies at DME. In cyclic voltammetric studies at HMDE one cathodic peak in lower scan rates and two cathodic peaks in higher scan rates were obtained along with an inverted peak in solutions of pH 2.1-7.1. Cyclic voltammetric studies at MCPE leads to one cathodic peak in solu- tions of pH 2.1-7.1 and two cathodic peaks in pH range of 8.1-10.1 along with an anodic peak in solutions of pH 2.1-7.1. A detailed comparison of results obtained in polarographic studies with those obtained in cyclic voltammetry at HDME and MCPE were presented in the studies.