The catalytic behavior of an HFAU zeolite was studied in the transformation of cholesterol, the most abundant sterol in the animal kingdom. It was found that such a catalyst is very active as of a temperature of 25 degrees C. After I h of reaction, about 50% of cholesterol was converted and 95% were transformed after 5 h. The first occurring reaction is dehydration leading cholestadienes as primary products. The secondary compounds arising from the transformations of cholestadienes identified in the reactional middle are cholestenes, diacholestadienes, spirocholestadienes and aromatics. On the other hand, among the trapped compounds in the cavities, it was identified oxygenated compounds (mono- and dioxygenated molecules) and aromatics, too. A synthetic scheme of cholesterol transformation over HFAU zeolite at ambient temperature was proposed from the evolution of identified reaction products. (c) 2006 Elsevier B.V. All rights reserved.