The electrochemical behavior of ethylene on PANI/Pt and Ag/PANI/Pt modified electrodes was investigated in different media. Morphology of the deposits of PANI were observed by SEM analysis, complemented by the EDX techniques to obtain the Ag composition that shows that Ag is deposited in the polymeric matrix which covered the whole platinum surface. The electrodic system comprising Ag/PANI/ Pt electrode exhibited a more important electrocatalytic response for ethylene oxidation in neutral solutions than the PAN/Pt and Pt electrodes at 20 o C.The results suggest that the oxidation of ethylene on Ag/PANI/Pt electrode is limited by adsorption-controlled reaction while the oxidation at PANI/Pt is mass transport-limited.