Dimerization of 2-methyl-l-butene and 2-methyl-2-butene mixture using Amberlyst 35, Amberlyst 15, Amberjet 1500H, Purolite CT-175 and Purolite CT-275 as catalysts was carried out in a discontinuous stirred tank reactor at 353 K in methanol and ethanol presence in a molar ratio isoamylenes/alcohol = 9. Amberlyst 35 was found to be the most active resin. Alcohol presence appeared to improve the selectivity for diisoamylenes: no significant amounts of trimers, tetramers or cracking products were obtained in the studied conditions. Almost all the alcohol react in the first reaction stages to form ether. Both alcohols gave the same correlation between isoamylenes conversion and diisoamylenes selectivity: as conversion increases, selectivity increases, diisoamylenes yield and isoamylenes conversion being lower in ethanol than in methanol presence. 2,3,4,4-tetramethyl-1-hexene, 3,4,4,5-tetramethyl-2-hexene and 3,4,5,5-tetramethyl-2-hexene- were the main dimers obtained. (c) 2005 Elsevier B.V. All rights reserved.