Linear (1-arm) and star-shaped (4-, 6-, and 16-arm) poly(D,L-lactide)s (PDLLs) were synthesized by ring-opening polymerization in bulk of D,L-lactide monomer. Hydroxyl end-group compounds and stannous octoate were used as the initiator and catalyst, respectively. The intrinsic viscosity and glass transition temperature (Tg) of the PDLLs decreased steadily as the branch arm number increased for similar molecular weights. However, the intrinsic viscosity and Tg values of the linear PDLL were less than the star-shaped PDLL for similar each PDLL arm lengths. Ibuprofen, a poorly water soluble model drug was entrapped in the PDLL microspheres. All drug-loaded PDLL microspheres were prepared by the oil-in-water emulsion solvent evaporation method, were spherical in shape, and had a smooth surface with fine dispersibility. In vitro drug release behaviors indicated that the drug release from the microspheres with higher branch arm number was faster than from those with lower branch arm number. Moreover, the drug release from the star-shaped PDLL microspheres was slower than that of the linear PDLL microspheres for similar PDLL arm lengths. The drug release behavior could be adjusted through both the branch arm number and arm length of PDLL. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012