Zeolite beta was hydrothermally synthesized using the method reported by Camblor et al. [M.A. Camblor, A. Corma, A. Misud, J. Perez-Pariente, S. Valencia, Stud. Surface Sci. Microporous Mater. 105 (1997) 341]. The influence of template agent, aluminum content and gel dilution on the crystalline size of zeolite beta was carefully studied. When the crystalline size reduces from 500 to 30 nm, the pore volume particularly the mesopore volume of zeolite beta significantly increased. The experimental results also evidenced that more template agent employed in the initial gel resulted in smaller crystalline sizes of zeolite beta whereas the water content has little effect on the crystalline size. This is the first work that demonstrates the important role of the template content in the initial gel in the determination of the crystalline size of nanosized zeolite beta. (C) 2006 Elsevier Ltd. All rights reserved.