The reaction of monohalonaphthalenes with potassium t-butoxide in a t-butyl alcohol-dimethyl sulfoxide (DMSO) mixture has been studied. The 1-bromonaphthalene reaction was extensively studied. Fifteen identifiable products were observed and conditions were found where the desired products, 1- and 2-t-butyl naphthyl ethers (V and VI) were formed in maximum yield, and their decomposition products, 1- and 2-naphthol (XIV and XV), were formed in minimum yield. The mole percent ratio of 1-substituted products (V and XIV) to 2-substituted products (VI and XV) was found under standardized conditions to be 0.35 ± 0.03 in every case when the halogen was I, Br and Cl. This strongly suggests that 1,2-dehydronaphthalene is an intermediate in each of these reactions. The fluoronaphthalenes were found to undergo only direct nucleophilic substitution with no formation of 1,2-dehydronaphthalene. The order of addition of base and alcohol to DMSO appears to be critical in this reaction. When t-butoxide is added first, the major products are 1- and 2-methylthionaphthalene and not V, VI, XIV and XV.