Given their sensitive tempera technique and the harsh tropical climatic conditions to which they are exposed, the conservation of the traditional mural paintings of Thailand is an extremely complex and difficult task. Their origin and evolution are studied and what are believed to be the traditional techniques because they were still in use earlier in this century are discussed. The state of mural painting conservation in Thailand differs from that of most countries in that there is an enormous quantity of them. Twelve official state conservators are assisted by teams of newly trained technicians. A program of technical collaboration with the Department of Fine Arts of Thailand has been arranged by ICCROM, supported by the Ford Foundation, with additional assistance from the Federal Republic of Germany, and has taken many forms: courses and seminars, individual training programs, provision of materials and equipment, on-site technical expertise, etc. During the course of this project, several new and important techniques for the preservation of mural paintings located in a tropical climate have been developed, successfully employed and documented, and are being taught to mural painting conservators who come from all over the world for training at ICCROM.