The effects of the irradiation intensity, irradiation time and illumination pattern of ultraviolet radiation on the mechanical and rheological properties of linear low density polyethylene (LLDPE) have been studied. For that purpose statistical experiments have been designed to study the effects of these variables on tensile properties of extruded LLDPE films. It has been found that the tensile strength, modulus of elasticity and elongation at break all decrease when LLDPE films are subjected to high intensity patterned irradiation. Conversely, low intensity patterned radiation causes the average tensile strength and the average elongation at break to increase. Rheological measurements suggest that these changes are correlated with changes in the molecular architecture of the films. The interaction between the illumination pattern and high intensity radiation causes the material to degrade as evidenced by a decrease in the zero shear viscosity of the resin. However, when the resin is subjected to low intensity patterned radiation, the zero shear viscosity increases while the slope of the shear thinning region decreases. This suggests that the illumination pattern causes the weight average molecular weight of the resin to increase and the molecular weight distribution to become broader.