MCM-41 materials were synthesized using cetyltetramethylammonium bromide (CTMABr) as the template and two types of silicas: regular silica-gel and colloidal fumed silica. The synthesis was made under hydrothermal conditions at 100 degreesC by adjusting the pH of the hydrogel to 10. A small amount of the sample was taken after each pH adjustment and analyzed by high-resolution thermogravimetry in order to determine the temperature ranges related to water desorption, surfactant decomposition and silanol condensation for the mesostructures studied, as well as to estimate their overall quality. The BET specific surface area and pore size distribution for calcined MCM-41 materials were evaluated from nitrogen adsorption isotherms.