In this study, four oil-shale samples (Nigde-Ulukisla) excavated from Central Anatolia Turkey were analyzed where this region is believed to have a high potential of oil in its shale rich outcrops. The samples (similar to 40 g) were combusted at 50 psi gas injection pressure, at an air injection rate of 1.5 L min(-1) in a combustion-reaction cell. All the experiments were conducted up to 600 degrees C. The percentages of oxygen consumption and carbon monoxide and carbon dioxide production were obtained instantaneously with respect to time. The combustion periods and relative reaction rates were determined by examining the effluent gas concentration peaks. Activation energies of the samples were determined using Weijdema's approach. It was observed that the activation energies of the samples are varied between 22-103 kJ mol(-1).