A reactive extrusion (REX) process has been developed for the chemical modification of a low-density polyethylene (LDPE) resin using a small amount of peroxide. Experiments have been performed according to a central composite statistical design using a twin screw extruder equipped with an inline wedge die rheometer. The modified materials have been analyzed in terms of their rheological properties, molecular weight distribution (MWD), and gel count levels. The results have shown that the MWD may be broadened while minimizing gel content and maintaining a melt index above a minimum value. Response surface analysis of the data has shown the peroxide concentration to be the most significant process variable for the range of conditions used. In addition, the statistical analysis has revealed significant correlations between the weight-average molecular weight and consistency index and between power law index and the high molecular weight tail of the MWD.