The buildings and stelae from the Maya period at Copan suffer from considerable decay. They consist of different types of local andesites which are transformed by humidity and the action of salts. Intensive biological activity alters and discolors the surface. After examination of the decay at the site and in the laboratory, techniques for the removal of the lichens and the consolidation of the stone have been proposed. A test program shall give evidence about the efficiency and durability of the chosen products under the climatic conditions of Central America. -- AATA