Mesoporosity has been introduced into the micron-sized pore walls of diatoms. The technique used involves dissolution and rearrangement of diatomaceous silica, via interactions with the surfactant hexadecyltrimethylammonium bromide. The resulting biomineral possesses ordered hexagonal and disordered mesostructure, and has a BET surface area of 284 m(2) g(-1). Electron microscopy, X-ray diffraction and nitrogen adsorption studies have been used to confirm the presence of mesoporosity in the material, and the stability of the micron-sized diatom architecture under the reaction conditions. (C) 2004 Elsevier B.V. All rights reserved.