Ethane and methanol are converted simultaneously over Ga/H-ZSM-5, Mo/H-ZSM-5 and Ga-Mo/H-ZSM-5 to produce light olefins and aromatics. The presence of methanol in the reactant stream is intended to facilitate activation of ethane following literature reports on co-conversion of methane and methanol. However, the conversion of ethane actually decreases significantly when methanol is present. To gain insight into mechanistic details, C-13-labeled methanol is co-converted with unlabeled ethane. These isotopic labeling studies show that carbon atoms from ethane and methanol are mixed in the products and in the carbonaceous compounds deposited on the catalysts. This indicates that both reactants take part in the formation of the hydrocarbon pool, which is the origin of all products.