Adult intussusception is a rare condition. Most of the cases are due to an organic lesion and unlike the incidence in children idiopathic forms are really exceptional, occurring at a rate of 5% of all cases. Whereas in children a main cause is seldom found, adult intussusception is usually characterised by the presence of a leading intraluminal benign or malignant lesion. The authors report their experience with a clinical case of ileocolic intussusception occurring in an 28-year-old white male. In spite of the patient's age, the clinical presentation was very typical with the classic triad of abdominal pain, blood per rectum and a palpable mass. Diagnostic tools, namely US and TC scan, together with colonoscopy confirmed the physical examination, so that surgery was initiated with a definite diagnosis of intussusception. A large polyp or a lymphoma were considered the possible leading causes. After right hemicolectomy, pathology revealed that there was no organic lesion and the bulging mass was caused only by oedema and haemorrhagic infiltration of the invaginated loop. The patient had been on antipsychotic drugs for several months and the possible explanation of the pathology was linked to altered peristalsis induced by the pharmacological agents he was taking. The authors compare their experience with the data reported in the literature, evaluating in particular the incidence, pathology, clinical presentation, diagnosis and treatment of adult intussusception.