Poly(aryl sulfone) belongs to a group of polymers with a very low crystallizabilities which include polycarbonates, polyether imide and polyarylate. When subjected to high temperature gradients in such processes as injection molding and melt spinning, this class of polymers vitrify into glassy form. However their processing-property relationships are quite different from those conventional amorphous materials such as atactic polystyrene (a-PS) and atactic poly(methyl methacrylate) (a-PMMA). These new polymers being already highly ductile materials do not undergo brittle-ductile transition when oriented beyond a critical orientation levels which is typical of a-PS and a-PMMA. The chemical structure of poly(aryl sulfone) chain is mainly composed of para linked phenyl groups and this gives rise to high optical anisotropy in the chain. With small levels of orientation large optical birefringences are attained in the fibers. This polymer was also found to obey the stress optical law which states that there is a linear relationship between the stress at the vitrification and the birefringences developed in the fibers. Beyond a critical stress level around 10(8) dynes/cm2 deviation from this linearity is observed. This deviation from linearity may possibly be related to onset of structural ordering that takes place at high orientation levels. The mechanical properties were found to correlate quite well with the spinline stress and modulus, yield stress and tensile stress were found to increase and elongation at break was found to decrease with increasing orientation.