The use of two kinds of tantalum(V) aminopyridinato complexes, bis(2-benzylamino-pyridinato)trichlorotantalum(V) and trichlorobis [2,6-di(phenylamino)pyridinato-N,N']-tantalum(V), activated by methylaluminoxane was studied in polymerization of ethylene. The activities of these homogeneous catalyst systems are comparable lo those of metallocenes. The weight-average molecular weights ((M) over bar(W)) of the produced polyethylenes are between 60000 and 200000 and (M) over bar(W)/(M) over bar(n) approximate to 2.