The pyrolysis studies of the Tarfaya (Morocco) oil shales were performed using an installation specially adapted to the pyrolysis of oil shale under microwave irradiation. The microwave cavity and the reactor were designed to assure a good transfer of the microwave energy to the material and, to study the pyrolysis of the oil shales. The results obtained revealed that this process can be efficiently used for the purpose. The formation of oil seems related to the dehydration of the shale and to the relaxation of pyrite and the products of the degradation of the kerogen. Ln addition, the obtained oil has interesting characteristics. It is more maltenic, less polar and contains less sulfur and nitrogen than the oils obtained by conventional pyrolysis. (C) 2000 Elsevier Science Ltd. All rights reserved.