Diphyllobothrium latum larvae in Perch (Perca fluviatilis) caught in Italian-Suisse lakes, to determine the infestion degree of the Plerocercoisis, has been inquired. This parasitosis is responsable for a zoonoses known as Diphyllobothriasis or Bothriocephaliasis.The results show that 1.5% infestion degree in 1989 has gradually increased up to the present 7 .8%. The survey can be completed by doing a systematic faeces test on coastal inhabitants. As the diet habits are gradually changing, freshwater fish products should be controlled by the veterinarian with greater attention.