A start-up procedure for use in the disproportionation of co-fed hydrogen and toluene feedstock over a nickel mordenite catalyst containing between 1.0 - 1.5 weight per cent nickel and having a silica to alumina molar ratio of between 16:1 and 22:1. At reaction start-up, the hydrogen to toluene molar ratio is maintained at an unconventionally low level of between 0.5 and 3.3. With an initial temperature of 250°C and under pressure of 550 psig or greater, toluene disproportionation is effected resulting in desirably high selectivity to benzene product and simultaneously low selectivity to undesirable non-aromatic compound by-product.