The Musée d'art et d'histoire of Geneva owns a Madonna and Child painted on a wood panel which dates from about 1340-1350. It was originally the central part of a triptych, bequeathed to the city of Geneva by Gustave Revilliod in 1890. The work was in poor condition: the panel was worn by woodworm and the painting itself had been altered by two different overpaints. Its attribution was thus made difficult. Eventually, it was recognized as a work of the Florentine, Jacopo del Casentino. A first attempt to restore the painting was unsuccessful. In 1975, because of its overpaints and the alteration of some colors, the laboratory was charged to examine it by scientific techniques. X-ray radiography revealed unexpectedly that the worm holes in the panel had been filled with white ground, prior to the application of the linen cloth under the painting. An authenticity problem then arose: Could a Florentine 17th-century master paint a Madonna and Child on an already worm-eaten panel? Analyses revealed that the original painting and the wood panel are genuine. They belong together. The wood panel was worm-eaten before it was painted, and the worm holes were filled while the white ground was applied. Examination by scanner showed clearly that, contrary to general opinion, the worm holes were not filled by injections from the back of the panel painting. -- AATA