New bicenter metal-complex catalysts supported on dehydrated microspheric silica gel have been synthesized and tested in the polymerization of ethene and butadiene. The catalysts contain two components : a titanium-magnesium- or chromium-containing compound and an oligodienyl metal-aluminium complexes with a bridge structure (metal - Zr or Ni). A possibility of preparation of linear medium-density polyethylene by polymerization of ethene in gas-phase process without using co; monomers was established. These catalysts also display high efficiency in the polymerization of butadiene, the products obtained being the mixtures of cis-and trans-polymers. It was found that titanium-magnesium catalysts modified by zirconium-organoaluminum compounds are most active in both ethene and butadiene polymerization processes.