Although the title La Gioconda appears on the Salai inventory and was later used at Fontainebleau, the case for accepting Vasari's claim that the painting is a portrait of Mona Lisa del Giocondo is not as strong as recent studies suggest. Critics who used the title before 1642 did not think that it referred to the surname of the sitter. A review of the evidence casts doubts on Vasari's credibility, but illuminates the unusual purpose of Leonardo's painting.