In this study, the fluorescein isothiocyanate (FITC)-albumin distribution, the amount of FITC-albumin release and the degradation of poly ( dl -lactic-co-glycolic acid) (PLGA) microspheres were evaluated. The higher the FITC-albumin concentration in the W 1 phase, the higher the protein concentration and loading efficiency in the microspheres, the larger the particle size of microspheres. Confocal laser scanning microscopy (CLSM) showed that the FITC-albumin was distributed uniformly in the microspheres with a low concentration while it was aggregated at higher concentrations. The high protein concentration in the microspheres showed significantly large initial release (above 70% w/w) during the 10 days. A higher PVA concentration in the W 2 phase resulted in a smaller particle size, higher protein contents and loading efficiency and decreased release rate. After a 10 day incubation period, the microspheres with a low FITC-albumin concentration had an almost spherical morphology, while microspheres with a high FITC-albumin concentration had a more distorted morphology, suggesting that rapid morphological changes and microspheres ruptures can be induced by an initial burst release.