Mucus from leech skin consists of mucin-like glycoproteins (designated as leech skin mucin) in association with several low molecular weight proteins and glycoproteins. A high molecular weight, heavily glycosylated protein fraction was isolated from leech skin by sequential chromatography on Bio-gel a-15m, Sepharose CL-2B. The isolated mucin comprsied about 80% carbohydrate and 20% protein. Threonine and Serine comprised 35% of the total amino acids while the oligosaccharide moiety contained glucosamine, galactosamine, fucose, galactose, glucose, mannose and sialic acid. Following alkaline borohydrate treatment, the carbohydrate chains were found to be linked O-glycosidically through threonine and serine. Leech mucin was analysed by CM52 cellose ion exchange chromatography and SDS PAGE. Its average molecular weight was estimated to about 480KDa.