A method is disclosed wherein t-butanol is reacted with methanol in a reaction zone in one step to provide methyl tert-butyl ether and the improvement in accomplishing the reaction which comprises:a. Using a catalyst consisting of a crystalline aluminosilicate faujasite Y-type zeolite which has been treated with a fluorophosphoric acid;b. continuously contacting said t-butanol and methanol in a molar amount of about 0.1 to 10 moles of methanol per mole of t-butanol with said catalyst at a temperature of about 20.degree. C. to about 250.degree. C. and a pressure of about atmospheric to about 1000 psig to obtain the methyl tert-butyl ether product.