Sodium alginate (NaAlg)/poly (vinyl alcohol) (PVA) blend microspheres (MS) were prepared by water-in-oil (w/o) emulsion method. These polymer microspheres were crosslinked with glutaraldehyde and loaded with metformin hydrochloride (MHC). The microspheres were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis to confirm the molecular dispersion of the drug, thermal stability, morphological properties, and crystallinity of the polymer matrix before and after blending. SEM of the microspheres suggested the formation of microspheres in spherical structure. Drug release data were analyzed using an empirical equation to understand the nature of drug transport through polymeric matrices. The controlled release (CR) characteristics of the polymer matrices was investigated in pH 7.4 media and from the results it was obtained that the drug was released in controlled manner up to 10 h. The physico-chemical properties of the microspheres were studied by calculating drug entrapment efficiency and drug release kinetics. Percent of encapsulation efficiency (% EE) decreased with increase in crosslinking agent (GA) and PVA content in the microspheres. The optimum % EE (80%) was observed in case of MS containing 40% of PVA with 15% MHC. The release profiles indicate that the release of MHC decreases with increasing the PVA/NaAlg (w/w) and drug/polymer ratio. At the end of 10 h, the highest release of MHC was found to be 96% for MS containing PVA/NaAlg (40 : 60) and 15 wt % drug loaded. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012