Vapor-phase alkylation of indole with methanol was carried out over HZSM-5 (30), HY, CeHY, LaHY. CrHY and CuHY zeolites in a continuous fixed-bed reactor at atmospheric pressure. Rare earth metal cation-modified HY zeolites are found to be more active for the alkylation of indole than HY zeolites and transition metal-modified HY zeolites. The maximum of 33.6% yield of 3-methylindole at 72.6% indole conversion was obtained over 3 wt.% CeHY catalyst at 300degreesC. Furthermore, the activity of pyridine-poisoned and calcined catalysts revealed that either Bronsted or Lewis acid sites of medium strength are the suitable sites for 3-methylindole formation.