This study aimed to systematically investigate the effect of organic loading on granule diameters, and on the composition of extracellular polymeric substances (EPS) in granules in various size-fractions at the beginning and end of the cycle of granular sludge sequencing batch reactor (GSBR). The organic loadings were 0.78 kg COD/(m(3).d) (GSBR1), 1.16 kg COD/(m(3).d) (GSBR2) and 1.53 kg COD/(m(3).d) (GSBR3). Granules with a diameter of 0.5-1 mm had the most stable EPS content and composition. The smallest granules had the largest amount of bound EPS. The amount of loosely-bound EPS increased as granule diameters decreased; it was lowest in the famine phase at end of the cycle. The proteins/polysaccharides ratio decreased below 1 only in soluble EPS in the famine period. In GSBR1, granules with a diameter < 0.5 mm predominated, and the increase in soluble EPS at end of the cycle was most substantial resulting in the lowest COD removal.