The paper describes oligomerization reactions of 1-hexene with catalysts derived from three metallocene complexes, Cp2ZrCl2, (CH3-Cp)(2)ZrCl2 and (n-C4H9-Cp)(2)ZrCl2, and two types of methylalumoxane. Gas chromatographic analysis of oligomers provides detailed information on the chemical structure of individual oligomer molecules, the chemical mechanism and kinetics of early stages of the oligomerization reactions.