Eosinophilic gastroenteritis is a rare disease of the gastrointestinal tract in which the eosinophils seem to play an important role in the inflammation of the gut wall. We report on a case with a synchronous first manifestation of eosinophilic gastroenteritis and bronchial asthma, which also occurred synchronously in all further episodes. The diagnosis was first made at the end of the second episode during which the patient lost more than 13 kg in weight. Under steroid therapy, symptoms of both diseases disappeared quickly in the third episode. We assume that participation of the gastrointestinal tract in patients with bronchial asthma occurs more frequently than expected. In asthma patients with abdominal symptomatology, eosinophilic gastroenteritis should also be considered.