A detailed kinetic model consisting of 132 free-radical reactions has been developed to describe the thermal cracking of tetralin. The model was tested against available experimental data for tetralin pyrolysis in the temperature range 350-500 degreesC. The importance of the knowledge of the impurity levels in the tetralin used for any experiment has been shown. The formation of the main products, namely, 1-methylindane, naphthalene, and n-butylbenzene, is correctly described. The production of 1-methylindane is due to the contraction of the saturated ring. Naphthalene is formed by dehydrogenation reactions. The production of butylbenzene is due to the ipso addition of a hydrogen atom to tetralin. When the temperature increases, the formation of 1-methylindane decreases, whereas those of n-butylbenzene and naphthalene increase.