Two endoglucanases (endoglucanase B and endoglucanase C ) without affinity for cellulose were purified from the culture broth of Cellulomonas sp. ATCC 21399 using gelfiltration and ion exchange chromatography. Fused rocket immunoelectrophoresis was used to select the fractions with t h e highest content of endoglucanase and lowest content of contaminating proteins. The endoglucanases were purified to immunological homogeneity. In addition both endoglucanases were homogeneous when analyzed by sodium dodecyl sulfatepolyacrylamide gel electrophoresis (molecular weights of endoglucanase B and endoglucanase C were 67000 and 25000, respectively). Endoglucanase B was homogeneous when studied by isoelectric focusing showing one protein band at pl 4.3. Both endoglucanases lacked activity against microcrystalline cellulose (Avicel) and showed similar endo action on carboxymethylcellulose (CMC). Endoglucanase B had a high specific activity against CMC, H,PO,-swollen Avicel and xylan, but showed no activity against galactomannan. In contrast, endoglucanase C showed activity against both CMC, xy-Ian, and galactomannan all being polysaccharide substrates linked with P-l-4-~-glucoside bonds. The specific activity of endoglucanase C against H3PO4-swollen Avicel was low.