Disproportionation of olefins has been investigated under selective conditions. The primary products from the reaction of 1-pentene are ethylene and n-octenes, and 2-pentene yields 2-butene and n-hexenes. From the mixed olefins, 1-pentene and 2-pentene, propylene, n-heptenes, 1-butene, and n-hexenes are primary products. A mixture of 1-pentene and 1-hexene gives ethylene and n-nonenes as initial products. From these results and consideration of molecular orbital symmetry conservation, it is proposed that the reaction proceeds via adsorbed cyclobutane. © 1969.