Eosinophilic gastroenteritis (EGE) in the adult is a distinctive pathologically-based disorder characterized by an eosinophil-predominant mucosal inflammatory process. Most often, the disorder is detected during endoscopic investigation for abdominal pain or diarrhea. Other causes of gastric and intestinal mucosal eosinophilia require exclusion, including parasitic infections and drug-induced causes. Occasionally, the muscle wall or serosal surface may be involved. EGE appears to be more readily recognized, in large part, due to an evolution in the imaging methods used to evaluate abdominal pain and diarrhea, in particular, endoscopic imaging and mucosal biopsies. Definition of EGE, however, may be difficult, as the normal ranges of eosinophil numbers in normal and abnormal gastric and intestinal mucosa are not well standardized. Also, the eosinophilic inflammatory process may be either patchy or diffuse and the detection of the eosinophilic infiltrates may vary depending on the method of biopsy fixation. Treatment has traditionally focused on resolution of symptoms, and, in some instances, eosinophil quantification in pre-treatment and post-treatment biopsies. Future evaluation and treatment of EGE may depend on precise serological biomarkers to aid in definition of the long-term natural history of the disorder and its response to pharmacological or biological forms of therapy.