Ga/ZSM-5 is an effective catalyst for the conversion of dilute (3%) ethylene-in-methane reactant streams into aromatic hydrocarbons at 500-550 degrees C. A Ga loading as low as 0.5 wt% is sufficient to obtain maximum yields of aromatic products. At 520 degrees C, an ethylene conversion of 93%, with an aromatics selectivity of 81%, was obtained over a 5 wt% Ga/ZSM-5 catalyst. The conversion of ethylene into aromatics over Ga/ZSM-5 catalysts involves a complex sequence of oligomerization, isomerization, cracking, and cyclization reactions that occur on Bronsted acid zeolites in the zeolite. The role of the gallium, which exists as both Ga3+ at zeolitic exchange sites and as Ga2O3 within the channels and on the external surface of the calcined catalyst, is to promote dehydrogenation of the acid-catalyzed oligomerization and cyclization products.