Abstract/Text: The aim of this study was to evaluate the clinicopathological spectrum of eosinophilic gastroenteritis and identify possible difficulties in establishing the diagnosis. All patients with a diagnosis of eosinophilic gastroenteritis, defined by the presence of gastrointestinal symptoms and eosinophilic infiltration of the gut (38), or a radiological diagnosis with peripheral eosinophilia (two), were identified from the Mayo Clinic records; in none was there evidence of extraintestinal disease. Patients were divided into three groups according to the Klein classification: predominant mucosal (23), muscular (12), or subserosal disease (five). A fourth group of patients (10) for comparison had abdominal symptoms and unexplained peripheral eosinophilia but no proven eosinophilic infiltration of the gut. It was found that a history of allergy was reported by 20 of 40 patients with eosinophilic gastroenteritis. Peripheral eosinophilia was absent in nine of 40. The patients with subserosal disease were distinct from the other groups in presentation (abdominal bloating, ascites), higher eosinophil counts and in their dramatic responses to steroid therapy. Otherwise the patients were similar regarding demographic factors, presenting symptoms (abdominal pain, nausea, weight loss, diarrhoea), and laboratory parameters. The ESR was moderately raised in 10 of 40 patients. The disease may affect any area of the gastrointestinal tract; eosinophilic infiltration was documented in the oesophagus in one patient and in the colon in two cases. Endoscopic biopsies missed the diagnosis in five of 40 presumably because of patchy disease. Eosinophilic gastroenteritis should be considered in the differential diagnosis of unexplained gastrointestinal symptoms even in the absence of peripheral eosinophilia.