Eosinophilic esophagitis (EoE), an atopic disease of the esophagus, has become increasingly recognized over the last 15 years. The epidemiology of EoE has now been reported from many countries around the world. While the clinical diagnosis of this disease depends on the patient’s clinical manifestations, the final diagnosis should be made based on the histopathological examination of esophageal mucosal biopsies. In the diagnosis of EoE, to facilitate the appropriate treatment of patients, it is extremely important to precisely recognize the presence of eosinophils in biopsy specimens of the esophageal mucosa. If eosinophils are present, EoE patients should be referred to an allergist for appropriate management with dietary modification, pharmacological agents (including corticosteroids), and/or mechanical dilation of the esophagus. We herein present and recommend the use of direct fast scarlet staining for the easy and precise recognition of eosinophils in biopsy specimens of the esophageal mucosa, a technique that has been routinely used in our laboratory.