Modifications to the double bonds of plant oils were done by addition of alcohols, using the corresponding epoxides as intermediates. Both, crystalline and amorphous aluminosilicates were studied as catalysts and they were thoroughly characterized using Si-29 and Al-27 MAS NMR as well as FT-IR, XRD, inductive couple plasme atomic emission spectroscopy (ICP-AES) and nitrogen adsorption, to link catalyst properties to catalytic behavior. Alummosilicates where found to be suitable catalysts for the nucleophilic addition of alcohols to epoxidized oils. Zeolites with higher mesopores content, such as steamed ones, were more active because the active Bronsted sites are more accessible to the bulky substrate. Aluminosilicates in lamellar form. like clays of the type montmorillonite, showed to be the most active alummosilicates for the epoxide alcoholysis. Clays with a higher de rce of Al3+ substitution for Si4+ in the SiO2 layers proved to be superior to those with a higher degree of Fe2+ or Mg2+ substitution for Al3+ in the Al2O3 layers. The analysis indicate that this better performance is due to a higher Bronsted acid strength present in the former clays. (C) 2003 Elsevier B.V. All rights reserved.