The present paper shows the preliminary data about the identification of Eustrongylides sp. larvae found in fish of the Trasimeno lake (Umbria) during 2015-2016. 100 specimens have been examined, 65 perches and 35 bleak. Visual examination has revealed larvae of nematodes in the musculature of 11 (16.9%) perches and 5 (14.3%) bleak, with an average infestation intensity of 1 and 2 parasites/host respectively. 10 larvae were subjected to morphological study, which allowed the identification as L4 larvae of Eustrongylides sp. Molecular analyses are underway in order to identify the species of the nematodes. Since the potential zoonotic role of Eustrongylides sp. and the growing tendency to consumption of raw or undercooked fish, is extremely interesting to study the epidemiology of the parasite not only in Trasimeno, but also in other lakes, in order to understand the mechanisms of transmission, provide apposite monitoring measures and apply appropriate sanitary measures.