The hydrodynamic properties of Aspergillus niger cellulase were determined at pH 7.0 using a Sephadex G-150 column. From the comparison of gel filtration behaviour, with those of standard proteins, molecular weight (39557), Stokes' radius (28.1 × 10-8 cm), diffusion coefficient (7.985 × 10-7 cm2 s-1) and frictional ratio (1.25) were calculated. The values suggest a globular conformation of the enzyme. © 2004 Elsevier Science B.V., Amsterdam. All rights reserved.