Abstract: An improvement in the fibril formation process which includes dissolving at an elevated temperature an olefin polymer having an inherent viscosity of at least 3.5 in a hot hydrocarbon solvent, shearing the hot polyolefin solution to thereby orient the polymer molecules therein, passing the sheared solution through a cooling zone maintained at a temperature well below the precipitation temperature of the solution while maintaining the orientation of the polymer molecules within the solution to thereby precipitate by thermal means the polymer solute of the solution in the form of a solvent swollen fibrous strand, separating a substantial portion of the polymer solvent from the fibrous strand, chopping and then beating the chopped fibrous strand in a liquid which is a nonsolvent for the polymer and which is soluble in the polymer solvent for a time sufficient to break down the fibrous strand into a plurality of fibrils, and separating the fibrils from the nonsolvent liquid.