The botanical sources and chemical compositions are reviewed of natural resins used, or likely to have been used, in the fabrication of objects of art and archaeology. They fall into two main chemical groups: those containing diterpenoids -- from the order Coniferales and from the Leguminosae family -- and those containing triterpenoids from several families of broad-leaved trees. Their chemical compositions, although liable to varying degrees of change with time and exposure, permit them to be identified more or less precisely in favorable cases. Examples of such identifications are described, mostly of conifer resins, using gas-chromatography.