Templated silicate films with mesoporous structure on the scale of 40 Angstrom grow at the air-water interface of concentrated surfactant solutions. X-ray reflectivity measurements show that the mechanism of this growth for our preparation involves two stages-the formation of an organized surfactant layer at the interface in the first 10 h and the subsequent rapid growth of a structure which shows strong diffraction associated with the mesoporous repeat distance. The structure appears to grow when the interfacial layer is complete with a thickness of about 30 Angstrom.