The thermodynamics and kinetics of the diethylbenzene-benzene transalkylation have been studied in liquid phase over faujasite Y in a batch reactor. The reactions were conducted at several temperatures between 423 and 513 K. The main product of the reaction was ethylbenzene. When the molar ratio of benzene over diethylbenzene was greater than five, a selectivity in ethylbenzene greater than 90% was found. The initial rates showed that the transalkylation reaction followed a first order mechanism. A kinetic model is proposed.