The t-butylation of naphthalene with t-butanol over different Y-zeolites and at different environments is reported. The zeolites investigated are H-Y, RE-Y and three US-Y samples with different Si/Al ratios. Though, as expected, increasing the reaction temperature (160-180 degreesC) increases naphthalene conversion, increasing the TBA/naphthalene mole ratio beyond 2 results in a decrease in conversion, presumably due to poisoning by the larger amount of water produced during dehydration. Both activity and yield of dialkylnaphthalenes increase on RE exchange and dealumination of H-Y. Higher conversions are obtained when the reaction is conducted under neat conditions than in the presence of the solvent cyclohexane or the added gas, N-2.