The role of the enolic hydrogen in the uncatalysed transesterification of malonates was examined. Equilibrium and kinetic measurements were made for the alcoholysis of diethyl malonate and a series of substituted malonates. The requirement for an enolic hydrogen, the first-order dependency of the rate upon the malonate, and the large negative values of entropy of activation are consistent with the uncatalysed transesterification proceeding through a cyclic enolate intermediate.