The simultaneous etherification and hydration of 2-methyl-2-butene and 2-methyl-1-butene were studied in a continuous stirred tank reactor (CSTR). The heterogeneous liquid-phase formation of tert-amyl ethyl ether (TAEE) and tert-amyl alcohol (TAOH) was catalyzed by a commercial sulfonic acid ion exchange resin. Addition of a small amount of water to the feed, caused a marked drop in the overall olefin (isoamylenes) conversion and in the etherification rate. The measured reaction rates of the etherification and alcohol formation were fitted to kinetic models of Langmuir-Hinshelwood type. These models are based on single site adsorption of every component and the surface reaction being the rate limiting step. The activation energies for the simultaneous etherification and hydration of isoamylenes were 117.7 end 79.9 kJ mol(-1), respectively. The activation energy obtained for the etherification corresponds well with the value of 108 kJ mol(-1) obtained in the experiments without water for the etherification of beta-olefin (2-methyl-2-butene) with ethanol.