Abstract: A fibrillated strand is made by a method wherein first a mass of a powder of a high polymer is compressed into a substrate having a density smaller than that of the high polymer and having a multiplicity of gas-filled voids. Then an intense heat beam is played on the substrate to melt the high-polymer powder and simultaneously heat the gas of the voids to explosively enlarge same while the beam and substrate are relatively displaced so that the substrate is melted along a path. The substrate is cooled at least at the path after irradiation by the beam to form a porous strand extending along the path in the substrate. This strand is separated from the substrate and is then at least uniaxially stretched. The beam is a CO.sub.2 TEM.sub.oo -mode laser beam and the method further comprises the step of focussing the laser beam on the substrate. The fused strand of the substrate is cooled so rapidly that it is normally not melted all the way through from top to bottom and from side to side.