The kinetics of the reaction of ethylene oxide in dilute aqueous solution at 25°C. with di- and tri-ethylamines, aniline, and pyridine have been investigated over a wide range of hydrogen and hydroxyl ion concentrations. The rates for all four amines were found to be very similar and were accurately expressed by the simple second order equation −d oxide/dl = k(oxide)(amine). The results indicate that basic catalysis does not occur and that catalysis by hydrogen or ammonium-type ions, if it occurs at all, is of no significance in the pH range 4–14.