Clay-modified electrodes were prepared with montmorillonite K10 and characterized in their ability to enhance the electrogenerated chemiluminescence (ECL) in a solution containing luminol and hydrogen peroxide. Montmorillonite K10 proved to be an effective catalyst for such a purpose : according to the anodic current and ECL intensity measured with the electrodes with and without clay particles. Under optimum conditions (pH 10 and 0.8 V vs. SCE), the ECL was enhanced by a factor of 10. Control experiments showed the enhanced ECL is likely due to a facilitation in the oxidation of luminol and H2O2 by the iron species contained in the clay. Double-step potential techniques suggested that superoxide is very likely to be the key reactive oxygen species involved in the clay-enhanced ECL reaction. In addition, clay/luminol/GOx electrodes were constructed by using aminopropyltrimethoxysilane as an immobilizing agent for the detection of glucose. Although the electrode sensitivity decreased by ca. 15% after 10 days, a linear calibration curve was attained, covering the concentrations of glucose from 10 mu M to 0.5 mM with a detection limit at ca. 10 mu M at pH 10.