Fecha de publicación: 27/03/1996 Fuente: WIPO "miel" The present invention relates to components of catalysts for the polymerization of olefins comprising a metallo-cene compound and a magnesium halide which have particular values of porosity and surface area. In particular the components of the invention have surface area (BET) greater than about 50 m2/g, porosity (BET) greater than about 0.15 cm3/g and porosity (Hg) greater than 0.3 cm3/g, with the proviso that when the surface area is less than about 150 m2/g, the porosity (Hg) is less than about 1.5 cm3/g. The components of the invention are particularly suitable for the preparation of catalysts for the gas-phase polymerization of a-olefins.