An estimate of the light-stability of unstabilized and stabilized polyamide textile fibers is presented. Results were obtained in the kinetic region of photooxidation by a viscometric method of quantitative evaluation of the efficiency of light-stabilizers, based on measuring the quantum yield of breaks in the main chain of the polymer molecule. The data obtained are compared with the generally accepted estimate of light-stability from the chain in mechanical strength properties of the specimens. -- AATA