Gas-phase alkylation of catechol with methanol on gamma-alumina and modified gamma-alumina catalysts is studied experimentally. By limiting the conversion to X < 0.3, the formation of polymethylated species can be avoided and only the three isomers guaiacol, 3-methylcatechol and 4-methylcatechol are observed. Optimising the catalyst composition and the reaction conditions, a selectivity of 0.75 for the industrially most valuable product 3-methylcatechol can be obtained.