Abstract: A material including filaments, which include a metal and an essentially coaxial core, each filament having a diameter less than 6 .mu.m, each core being essentially carbon, displays high effectiveness for shielding electromagnetic interference (EMI) when dispersed in a matrix to form a composite material. This matrix is selected from the group consisting of polymers, ceramics and polymer-ceramic combinations. This metal is selected from the group consisting of nickel, copper, cobalt, silver, gold, tin, zinc, nickel-based alloys, copper-based alloys, cobalt-based alloys, silver-based alloys, gold-based alloys, tin-based alloys and zinc-based alloys. The incorporation of 7 percent volume of this material in a matrix that is incapable of EMI shielding results in a composite that is substantially equal to copper in EMI shielding effectiveness at 1-2 GHz.