Exploration of the Medici chapels in San Lorenzo in Florence revealed the burials of nine infantile members of the Medici family. Eight children were found in the intact tomb of the last Grand Duke Giangastone (1671- 1737). The crypt contained several small coffins collapsed to the floor or randomly spread over a raised plank, as a result of the disastrous flood of the Arno river in 1966, which partly upset the tomb and left a layer of dry mould. The children's remains, mostly skeletonised, were found inside the coffins or scattered on the floor or on the plank, probably transported by the water. Another child was exhumed from the chapel of Grand Duke Ferdinand I (1549-1609) and Cristina from Lorena (1565-1636). The infantile remains were submitted to anthropological study, which allowed to establish the number of individuals buried in the crypt, and to estimate the age at death. The anthropological results were compared with information provided by archival documents, related to members of the family who died in infantile age. An identification of the children is proposed.