Urea inclusion compound (UIC) formation was used to fractionate carbohydrate polymers, poly-L- and poly-DL-lactic acid, by molecular weight. The UIC fractionation process employed was rapid, simple, scalable, and may have potential for use in preparative- and large-scale purification of polymers. Differential scanning calorimetry measurements reflect the formation of UICs for both polymer types. Under the conditions employed, the resultant UIC-rich solid phase contained polylactic acids of molecular weight distribution similar to the process feed sample, whereas the solvent-rich phase contained polymer of significantly lower molecular weight. The difference in molecular weight increased with the average molecular weight of the polymer and the degree of incorporation of polymer in the solid phase, and was greater for poly-D,L-than poly-L-lactic acid. The distribution of urea between the solid and the solvent-rich phases was independent of the molecular weight of the polymer or stereochemistry for a given polymer-urea-solvent ratio in the mixture.