On two examples, the restoration of a big Bodhisattva sculpture in Sri Lanka and the work on an ancient Maya site in Honduras, it is demonstrated that in the tropical climate various destructive agents are effective in attacking the stone. A thorough analysis of the causes of decay is necessary to find out the most effective methods for conservation. Of particular importance in the tropical climate is the application of preventive methods, acting against the destructive forces, for the usual methods of surface protection and impregnation for consolidation does not prove to be of a long lasting efficiency in these regions. Most of the damage on stone in tropical countries is due to the action of humidity, bringing salts from the ground into the stone, dissolving its surface, weakening its strength by an accelerated weathering of the minerals and causing the growth of microorganisms and vegetation on the surface. If a permanent survey of the object by cleaning and reapplying hydrophobing coatings is not possible, effective technical means are necessary to prevent humidity from entering into the stone. See also AATA 13-845 and 16-1241.