Isomerization and dimerization of linear alkenes under isobutene dimerization conditions with tert-butyl alcohol as the selectivity-enhancing component were studied in experiments with pure 1-butene and cis-2-butene feeds and with a mixture of isobutene and cis-2-butene. Conversion of cis-2-butene to 1-butene was low, but both linear butenes were found to isomerize to trans-2-butene, especially at high temperatures and low tert-butyl alcohol concentrations. Codimers of isobutene and 2-butene were formed in the experiments with the isobutene-cis-2-butene mixture. Isobutene conversions were a little higher in these experiments than in the experiments with the pure isobutene feed, while the selectivities for the dimers were about the same. Kinetic modeling of the data was carried out, and a Langmuir-Hinshelwood-type kinetic model was constructed for the codimerization reaction.