On the basis of a case of adenocarcinoma of the small intestine which brought to their attention, the authors analyse the etiopathogenetic and clinical aspect of these tumours in the light of the international literature. In particular, they focus on the difficulty of making an early diagnosis due to the fact that the initial symptoms are vague and aspecific and instrumental tests often do not allow a differential diagnosis to be made between adenocarcinoma and chronic inflammatory disease of the small intestine, benign tumours and other neoplasias. Lastly, the authors underline the prime role of surgery in the treatment of this form of cancer despite the fact that the concept of oncological radicality is drastically reduced in relation to the lymphoglandular layout of the jejunum and ileum since it should include the sacrifice of the superior mesenteric artery with imaginable consequences.