The coupling of methanol and isobutanol was carried out over selected acid catalysts. An amorphous silica-alumina, a zeolite and aluminas were tested as catalysts of the coupling. The correlation between the catalysts acidity and their activity and selectivity was studied. The catalytic tests were carried out in a fixed-bed flow microreactor working on line with a gas-chromatograph. The acidic properties of the catalysts were followed by IR studies of pyridine adsorption. The results obtained proved that the strength and the concentration of acid sites on the catalysts surface effected the alcohols conversion to ethers. It was found that the undesirable dehydration of isobutanol to isobutene was catalyzed by stronger acid sites than those required for the etherification reaction.