A cellulase [endo-b-1,4-D-glucanase (EC )] was iso-lated from the hepatopancreas of abalone Haliotis discus hannaiby successive chromatographies on TOYOPEARL CM-650M, hydroxyapatite and Sephacryl S-200 HR. The molecular mass of the cellulase was estimated to be 66 000 Da by SDS/PAGE, thus the enzyme was named HdEG66. The hydrolytic activity of HdEG66 toward carb-oxymethylcellulose showed optimal temperature and pH at 38 Cand , respectively.