The purpose of the present article is to provide a perspective of constitutive equations for glassy polymers developed using the molecular chain network theory. The results of experimental observations of the deformation behavior of glassy polymers at macro- and microscale are indicated, and an accommodation of the characteristic feature of deformation behavior into the molecular chain network theories is discussed. The related computational simulations of neck formation and its propagation under plane strain and three-dimensional conditions are illustrated. The results clarified the three-dimensional characteristic feature of neck propagation behavior under isothermal condition and the effect of deformation-induced heat and pre-drawing on the plane strain neck propagation behavior.