We will briefly state the basic advantages of crazing in comparison to traditional methods of adding modifiers to polymer films and fibres: the modifier is incorporated in the bulk of the polymer not by diffusion but by viscous flow of the modifier solution over the system of micropores characteristic of the structure of the craze. Since the transport rate by viscous flow is much higher than in diffusion, the rate of modification by crazing is high enough for continuous, high-speed incorporation of low-molecular-weight additives in drawing the polymer in liquid media. It is actually possible to combine orientation drawing of the polymer with addition of the modifiers. It is very important that it is not necessary to create new equipment to do this, as existing equipment for drawing polymer fibres and films can be used after insignificant modification; since a strong intermolecular interaction between polymer and additive is not required for fixing the additive in the structure of the fibre, the assortment of additives can be infinitely expanded. In particular, since the process is conducted at room temperature, there are no limitations in incorporation of thermally unstable additives, which also increases the selection; it is in principle possible to incorporate any combination of modifiers (for example, fireproofing compound and dye, etc.) in polymer fibres in one operation.