Nostoc flagelliforme cells were studied with regard to the physico-chemical characterization of the extracellular polysaccharides (EPS) secreted in a liquid suspension culture. The hydrolyzed EPS were determined to be composed of four neutral sugars, which were glucose (43.2%), xylose (20.6%), galactose (29.9%), and mannose (6.3%). The glucuronic acid was the only uronic acid identified in the residue. The apparent molecular weight was estimated at $2.79{ imes}10^5$. The Fourier transform infrared spectra showed that the EPS evidenced characteristics typical of non-sulfated polysaccharides. The UV spectrum and Bradford reaction indicated that there were no nucleic acids and proteins in them. The thermal analysis showed a decomposition peak at $245^{circ}C$ on the thermogravimetric (TG) curves. The scanning electron microscope (SEM) analysis indicated that the EPS possessed a porous structure. The observed microstructural irregularities indicated that the polysaccharide was a type of amorphous solid. These results showed that the EPS of N. flagelliforme cells might be employed as a substitute for those normally derived from field colonies. The results of this study may prove to be beneficial to the protection of the natural resource represented by N. flagelliforme.