A simplified kinetic model of carbonate sediment diagenesis is presented. Although based upon the assumption of first order reactions, the steady-state development of the model is independent of reaction order. The model is shown to be compatible with the results of laboratory investigations of reactions between both seawater and distilled water and mixed carbonate assemblages. The consequences of the steady-state model are in close agreement with field observations in carbonate environments and afford a possible explanation of the supersaturation of tropical marine surface waters, selective solution of metastable mineral phases and the mineralogical differences between modern carbonate sediments and ancient limestones. The slow evolution of excess carbon dioxide from aqueous solution is shown to be an important contributing factor in the diagenesis of carbonate sediments by this or any more refined kinetic model.