Abstract: A method for preparing C.sub.4 to C.sub.10 .alpha.-olefins having a major portion C.sub.6 .alpha.-olefins employing tri alkyl aluminum compounds, e.g., Al(C.sub.2 H.sub.5).sub.3 or Al(C.sub.4 H.sub.9).sub.3 or mixtures of Al(C.sub.2 H.sub.5).sub.3 and Al(C.sub.4 H.sub.9).sub.3 as well as the unmixed C.sub.2, C.sub.4 alkyl aluminum isomers or homologs in the growth step using added ethylene at about 120.degree. C., 500-700 psig, 5-90 minute contact time followed by displacement with C.sub.2 H.sub.4, C.sub.4 H.sub.8, or C.sub.2 H.sub.4 and C.sub.4 H.sub.8 to free the growth alkyl and regenerate the tri alkyl aluminum compounds. The growth .alpha.-olefins are separated with all of the C.sub.2 H.sub.4 recycled to the growth and displacement steps, and part or all of the C.sub.4 H.sub.8 recycled to the displacement step.