Abstract: The invention concerns an unsaturated ethylene copolymer, a method for producing the ethylene copolymer, and the use of the ethylene copolymer in compositions for producing cross-linked structures, such as material for electric cables. In the method, ethylene and at least one monomer which is copolymerizable with ethylene and includes a polyunsaturated comonomer having a chain of at least 8 carbon atoms and at least 2 non-conjugated double bonds, of which at least one is terminal, are polymerized at a pressure of about 100-300 MPa and a temperature of about 80.degree.-300.degree. C. under the action of a radical initiator. The polyunsaturated comonomer preferably is an .alpha.,.omega.-alkadiene having 8-16 carbon atoms, most preferred 1,9-decadiene. Apart from the polyunsaturated comonomer, polymerization may also involve another vinyl-unsaturated monomer, preferably containing at least one functional group selected from hydroxyl groups, alkoxy groups, carbonyl groups, carboxyl groups and ester groups.