polyolefinic compositions comprising : 1 - 99 % by weight of a propylene amorphous polymer , and 1 - 99 % by weight of a copolymer selected from a copolymer of propylene with ethylene and / or alpha - olefins c 4 - c 10 , and a composition comprising : 10 - 50 % by weight of an isotactic polypropylene with ethylene and / or alpha - olefins c 4 - c 10 ; 0 - 20 % by weight of a copolymer containing ethylene , insoluble in xylene , and 40 - 80 % by weight of an elastomeric copolymer of ethylene with propylene and / or alpha - olefins c 4 - c 10 , optionally with small amounts of diene . these compositions are endowed with good mechanical and optical properties and are suitable for the manufacture of articles for biomedical applications .