The causes of stone decay in tropical countries are compared to those in temperate climates and analyzed one by one: the chemical action of rain, whose acidity needs to be more systematically documented; the coarseness of the marble used in Sri Lanka which accelerates the growth of microorganisms; the physical attack by crystallizing salt; the rapid growth of mosses, lichens, algae, and related organisms; the decay due to wind-borne material; water condensation in cool caves; and tourism, plundering, and neglect. There is no reliable literature on the subject of the protection of stone against weathering relevant to the tropics; hydrophobing of the surfaces show short term good results. A number of treatments to counter plant growth are described and their efficiency evaluated. Long term observation together with laboratory studies are now necessary to find the most efficient techniques for the particular problems. Acknowledgements and a list of materials and suppliers are appended.