Sets forth the evidence of the 16th and 17th centuries on the condition of Leonardo's painting in S. Maria delle Grazie, Milan. The damage was almost immediately apparent; from the early 16th century the problems caused by humidity and by the technique of the painting have been discussed. Vasari, among others, believed that a copy was better than restoration. A copy commissioned from Andrea Bianchi for the Pinacoteca Ambrosiana, Milan, can give some help in reconstructing the condition of Leonardo's work in the early 17th century; some misreadings could be explained by deterioration of the painting. In 1674 it was noted that the work could be read in certain light. The first known restoration is Michelangelo Bellotti's work of 1726.