Vapor-phase ethyl tert-butyl ether (ETBE) synthesis was carried out in a fixed-bed flow reactor in the presence of three different kinds of heteropolyacid catalysts and four different kinds of ion-exchange resins. An activity change in the order of silicotungstic acid > tungstophosphoric acid (Dawson) > tungstophosphoric acid (Keggin) was observed with heteropolyacids and Amberlyst 15 > Lewatit K-2629 > Amberlyst 35 > Amberlyst 16 with ion-exchange resins. In ETBE synthesis over heteropolyacid catalysts, diethyl ether and ethylene (valuable petrochemical feedstocks) formation was also observed at temperatures above 368 K. DRIFTS analysis of pyridine-adsorbed samples revealed changes in acidity in accordance with activity. The significance of Bronsted acidity on the catalyst activity was illustrated. The inhibiting effect of water on ethanol adsorption and hence the catalyst activity was demonstrated by interpretation of experiments conducted using Amberlyst-15. Conversion of diluted ethanol to ETBE in the presence of Amberlyst 15 was found to be higher than the results obtained with pure ethanol using Amberlyst 16 and Amberlyst 35.