The crested porcupine (Hystrix cristata L.) has been shown to have considerably increased in numbers and to have occupied new territories in Tuscany, which is the northernmost part of its range. New data on its ecology and biology, and the negative effects of an excessive density of these rodents on the rural and natural environment are reported. Since this species is protected by law in Italy, because of its high value from the faunistic point of view, some possible techniques, to be improved upon, for the capture and redistribution of live specimens are discussed