The kinetics of the hydrolysis of ethyl acetate in acetone-water and dioxane-water systems are reported. The rate constant passes through a minimum when the concentration of the organic solvent in the medium is in the neighbourhood of 80%. The temperature variation conforms strictly to the Arrhenius equation even for media containing extremely high proportions of organic solvent. Even though the activation energy is affected by changes in solvent composition, the variations are not sufficiently marked for an analysis. The frequency factor has got a tendency to follow the trend of activation energies.