The use of poly(lactic acid) (PLA) for controlled drug delivery applications was limited by unfavorable physical properties such as hydrophobicity, high intrinsic crystallinity, low permeability, and high glass transition temperatures. This research used polyethylene glycols (PEGs) of varying molecular weights (300-18,500 g/mol) and concentrations (0-50% w/w) to modify the permeability, intrinsic crystallinity, glass transition temperature, residual solvent levels, and release of a model drug, 5-flurouracil (5FU), from monolithic films and microcapsules fabricated with PLA. The films were fabricated by solvent casting from methylene chloride. The microcapsules were formed by a coacervation method by using a methylene chloride/hexane solvent/nonsolvent system. Compared to PLA films, all PLA: PEG films showed the following: (1) a glass transition temperature between 40 and 55degreesC, (2) 5-8% lower residual solvent levels, and (3) enhanced permeability to 5FU. These results suggested that the incorporation of PEG improves the physical properties of PLA films to enable fabrication of controlled release delivery systems. Similar to the films, incorporation of PEG also enhanced the permeability of PLA microcapsules to 5FU. However, high intrinsic crystallinity, dual endothermal character for PLA melting, and significant burst release of 5FU in PLA: PEG microcapsules may limit their development for controlled drug delivery applications. (C) 2004 Wiley Periodicals, Inc.