This study examined the production of cellulose nanocrystals from microcrystalline wood cellulose, Avicel and recycled Pulp of wood pulp using sono-chemical-assisted hydrolysis. Two hydrolysis systems: deionized water and maleic acid were evaluated. In deionized water, Avicel produced cellulose nanocrystals with average diameter of 21 +/- 5 nm (minimum 15 nm and maximum 32 nm). Cellulose nanocrystals from recycled pulp were not distinctively spherical and had an average diameter of 23 +/- 4 nm (minimum 14 nm and maximum 32 nm). Maleic acid (50 mM) sono-chemical assisted hydrolysis of Avicel at 15 degrees C and 90% power Output for 9 min produced cellulose nanocrystals which were cylindrical in shape and were of dimensions, length 65 +/- 19 nm and width 15 nm. (C) 2008 Elsevier Ltd. All rights reserved.