Technical Abstract: Cotton burr and cottonseed hull are relatively inexpensive natural renewable materials from cotton and cottonseed processing. Recently several new polymer applications have been reported involving these cotton byproducts. These new developments are briefly reviewed in this article. In the first application, the cotton byproducts have been used directly as fillers in poly(lactic acid) and low-density polyethylene composites. The composites have been prepared by melt blending and extrusion. The addition of these low-cost fillers has slightly changed the composite’s thermal properties but significantly affected the composite’s mechanical properties. In the second application, the cotton byproducts have been partly converted into cellulose esters without prior chemical breakdown or physical separation of cellulose, lignin, protein, and other components. The process entails treating these materials with acetic anhydride and iodine, with no solvent involved except during sample workup. In the third application, these materials have been partly converted into carboxymethyl cellulose and carboxymethyl xylan. The potential uses of these materials are also discussed.