Homogeneous Ziegler - Natta catalysts have been known since 1950s

but they have very low activities at that time. In 1980 it was found that using of oligomeric methylaluminoxane (MAO) as cocatalyst significantly increase the activity of the catalysts. The discovery made Ziegler - Natta catalysts in a state of renaissance and many new catalyst systems appear which can stereoselectively polymerize α-olefins and their derives. In this paper we present a review on the formation and development of homogeneous Ziegler - Natta catalysts.