Native petroleum resins from two Mexican crude oils have been fractionated using reversed phase chromatography (RPC) and adsorption chromatography normal phase chromatography (NPC). RPC with acetone/DCM and NPC with cyclohexane/DCM/acetone produced different resin fractions that were characterized by Fourier transform infrared (FT-IR) spectroscopy and gel permeation chromatography (GPC). Observable reduction in polydispersity was achieved for the resins with both systems. Chromatographic fractionation permits a more complete inventory of structural features in this kind of complex polar-hydrocarbon mixtures. (c) 2006 Elsevier Ltd. All rights reserved.