A number of nanosize mordenite (MOR) analogues with particle size ranging from 5 to 50 nm were synthesized by the hydrothermal method. The effect of various growth parameters like: alkalinity of the medium, type of silica source, etc. on crystal morphology and the crystal size of MOR type of zeolites was investigated. Specific surface and micropore volume were investigated by the Brunauer-Emmett-Teller (BET) rnethod. XRD, SEM, TEM studies indicate nanosize growth of the MOR type crystals. Electron diffraction patterns confirm the crystalline nature of the nanopaiticles and the results of their indexing prove that the material is MOR. These synthesized materials show microporous as well mesoporous character. In the case of MOR material synthesized using sodium silicate, it was found that an increase in the alkalinity of the medium led to changes in the Morphology and crystal size of the material. For low concentrations of NaOH, the crystallites were spherical in shape whereas at high concentrations, they were in the shape of nanorods of diameter 25 to 50 nm. The morphology of the MOR material synthesized using tetraethyl orthosilicate (TEOS), on the other hand, did not change when the NaOH concentration was increased beyond 2.0 molar. (C) 2008 Published by Elsevier Inc.