A gelling polysaccharide was extracted from Togekirinsai (Eucheuma serra), which was collected from Miyako Island, Okinawa Prefecture, Japan, and purified by gelation with calcium chloride. The purified polysaccharide obtained from Togekirinsai was colorles fibrous powder; yield, 38.3% (w/w) based on dried seaweed and 4.6% (wet seaweed). The total carbohydrate, ash and moisture contents of the polysaccharide were 71.4, 21.2 and 7.1%, respectively. The content of total sulfate was estimated to be 23.8%. The polysaccharide was composed of D-galactose, 3, 6-anhydro-D-galactose and ester sulfate at a molar ratio of 1.2: 1.0: 1.5. Molecular mass of the polysaccharide was estimated to be about 2.8×10⁵. The infrared spectrum and values of optical rotation of the polysaccharide at different temperatures were in agreement with those of standard ι-carrageenan. The ¹³C- and ¹H-NMR spectra showed the polysaccharide isolated from Togekirinsai was composed of D-galactopyranosyl-4-sulfate and 3, 6-anhydro-D-galactopyranosyl-2-sulfate . These results indicate that the gelling polysaccharide is a ι-carrageenan.