Copolymerization of ethylene with 4-methyl-1,3-pentadiene (4-MPD) catalyzed by 1,4-dithabutanediyl-linked bis(phenolato) titanium complexes I and 2 activated by methylaluminoxane (MAO) produced exclusively ethylene-4-MPD copolymers with high activity. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with 4-MPD content up to 83%. The resulting copolymer are crystalline as shown by thermal analysis and by the X-ray powder diffraction profiles. The microstructural features were fully elucidated by C-13 NMR spectroscopy revealing that the copolymers with various 4-MPD content show a strong tendency to the alternating microstructure which was confirmed by the kinetic elaboration.