Infant abandonment from the Middle Ages to the end of the nineteenth century has fixed the attentions of numerous historians. Several modern writers invoke the probability that married parents sometimes killed their newborn infants too. By looking closely at a specific community through a nominative study (that is, identifying each of the inhabitants by name and by family), and inserting the material into a district context treated statistically, it should be possible to know more about unreported infanticide by married couples. Judging from states of souls lists and baptismal registers, it appears that Tuscan parents practiced infanticide on some considerable scale. Even where the overall ratio of males to females seems close to the natural one, there may have existed counterbalancing forms of infanticide eliminating both girls and boys, but in different places and among different social groups, which is consistent with evolutionary theory. In bad years infanticide might have corresponded to a quarter or a third of live births. The practice may explain the gradual decline of population across much of Central Italy during the long 17th century, from 1590 to 1730.