The thermal cracking of n-butane was compared with both thermal and catalytic n-butane oxidative dehydrogenation reactions. It was found that thermal oxidative dehydrogenation of n-butane was highly selective to n-butenes (approximately 70%) in the conversion range of 11-20%. This reaction proceeded at lower temperature than the thermal cracking of n-butane without oxygen. These results suggest that both reactions have different initiation steps. In the thermal cracking of n-butane the reaction initiated by the C-C bond scission, whereas for the thermal oxidative dehydrogenation of n-butane the removal of the hydrogen atom by the molecular oxygen to form (C) over dot(4)H(9) and H(O) over dot(2) radicals was proposed as the main initiation step. On the other hand, butadiene was only obtained via a catalytic pathway, being strongly dependent on the reaction conditions.