Copolymerization of ethylene (E) with 2-methyl-1-pentene (2M1P) took place with rather efficient 2M1P incorporation by using the Cp*TiCl2(O-2,6-(Pr2C6H3)-Pr-i) (1)-MAO catalyst system, whereas the 2M1P incorporations by the Cp2ZrCl2, [Me2Si(C5Me4)((NBu)-Bu-t)]TiCl2, Cp'TiCl2((NCBu2)-Bu-t) [Cp' = Cp (3), Cp* (4)], and Cp*TiCl3-MAO catalyst systems were negligible under the same conditions. The effects of substituents in both the cyclopentadienyl and the aryloxide ligands toward the catalytic activities and the 2M1P incorporations were explored, and use of both Cp* and 2,6-diisopropylphenoxy ligands was found to be important to obtain poly(ethylene-co-2M1P)s with rather efficient and uniform 2M1P incorporations as well as with notable catalytic activities. No distinct differences in the 2M1P incorporations were seen in the copolymerization by 1 in the presence of various cocatalysts [methylaluminoxane (MAO), methylisobutylaluminoxanes (MMAOs), borates], and the nature of ligands directly affects the 2M1P incorporation. Copolymerizations of ethylene with 7-methyl-1,6-octadiene (MOD) by 1,3,4-MAO catalyst systems proceeded at remarkable rates with efficient exclusive incorporation of monoolefins (without incorporating trisubstituted olefin), affording high molecular weight unsaturated poly(ethylene-co-MOD)s with high MOD contents. The MOD contents in the resultant copolymers in the ethylene/MOD copolymerization by 1,3,4-MAO catalyst systems were thus closely related to those in the ethylene/1-octene copolymerizations under similar conditions.