Preliminary report on the chemical composition of the pigments of Leonardos' Last Supper at S. Maria delle Grazie, Milan, with particular attention paid to the binding agents and the components of their alteration. The principal instrument of analysis is the infrared spectrophotometer, and the techniques to read both the sample and the layers below are described. Publishes detailed results of the first work, describing the chemical make-up of both soluble and insoluble components. There are great differences in composition even in a small sample, making further analysis indispensable.