Transformation of commercial C-7 and C-9 aromatic streams to xylenes over zeolite beta have been studied. These results have been compared with those obtained on other zeolites like ZSM-5 and mordenite. The effect of variations in reaction parameters like temperature, weight hourly space velocity (WHSV) and feed composition on xylene formation was considered. The trimethylbenzenes became disproportionated, while ethyltoluenes underwent de-ethylation followed by disproportionation of product toluene. The highest yield of xylenes was obtained with a feed consisting of nearly equal proportions of toluene and 1,3,5-trimethylbenzene. Lower WHSV and higher temperature enhanced the formation of xylenes.