This paper deals with the structural characterization of the Moroccan Timahdit (Y-layer) oil shale kerogen. For this purpose, the kerogen concentrate was submitted to stepwise hydrolysis under phase transfer catalysis conditions. The results show that aliphatic and aromatic dicarboxylic acids are involved in the cross-linking of the kerogen matrix, acting as bridges, while aliphatic and aromatic monocarboxylic acids, and alcohols represent monosubstituents of the matrix. Aliphatic mono- and dicarboxylic acids are produced on ruthenium tetroxide oxidation of the kerogen. These acids arise from a variety of reactions including cleavage of ester linkages. 17 alpha (H),21 beta (H)- and 17 beta (H),21 alpha (H)-hopanoic acids, probably bound to the kerogen by ether groups, were identified in the oxidation products. (C) 2001 Elsevier Science Ltd. All rights reserved.