The regioselectivity (selectivity for 1-butene) of gel-immobilized nickel complex catalyst systems (Ni-GICS) in the ethylene dimerization reaction was studied, in which poly(4-vinylpyridine) (PVP), an interpolymer complex of poly(4-vinylpyridine) and poly (methacrylic acid) (PVP-PMA), a complex of poly(4-vinylpyridine) with gel-immobilized chlorine-containing organoaluminum compounds (PVP-GOAC), and a poly(methacrylamide) (PMAA) were used as macroligands. It was shown that 1-butene was the single primary product in all cases, undergoing to some extent isomerization to a mixture of 2-butenes with increasing ethylene conversion. At low conversions, cis-2-butene is mainly formed, while the relative amount of trans-2-butene increases with conversion. When the ethylene concentration in the system is maintained at a constant level, the amount of 1-butene in the product decreases, with increasing monomer conversion, to a certain steady-state value, which serves as a quantitative characteristic of the Ni-GICS regioselectivity. The latter depends on the nature of the macroligand and increases in the order PVP (20-25%) < PVP-PMA (30%) < PMAA (85-90%) approximate to PVP-GOAC (85-90%).