The ethylation of benzene with ethanol over USY zeolite catalysts has been investigated at three different temperatures (300, 350, and 400 degrees C) for reaction times of 3, 5, 7, 10, 13, and 15 s with constant benzene to ethanol mole ratio of 1:1. Significant benzene conversion was found in the ethylation of benzene with ethanol over USY-2 catalyst as compared with the negligible conversion observed over USY-1 catalyst of lower acidity. The cracking of ethylbenzene (EB) was found to dominate at high temperatures (350 and 400 degrees C) in the ethylation of benzene with ethanol over USY-2 catalyst while ethylbenzene ethylation becomes significant at lower temperature (300 degrees C). Considerable amount of toluene was observed in the ethylation of benzene over USY-2 catalyst and was found to increase with increasing reaction temperature. The effect of reaction conditions on ethylbenzene selectivity, toluene selectivity, toluene-to-EB ratio, and total diethylbenzene (DEB) selectivity, are reported. Kinetic parameters for the ethylation of benzene with ethanol (E-1), cracking of EB (E-2), ethylation of ethylbenzene with ethanol (E-3), and the cracking of diethylbenzene (E-4) over USY-2 catalyst were determined using the catalyst activity decay function based on time-on-stream model. The apparent activation energies were Found to decrease as follows: E-2 > E-3 > E-4 > E-1.