The present work was carried out on 40 specimens of oesophaguses of both sexes of catfish (carnivorous fish) and grass carp (herbivorous fish) in order to observe the morphological and histological differences between the two species. Oesophagus of catfish was divided into 2 parts: anterior and posterior ones. The anterior part of the oesophagus of catfish was characterized by the presence of numerous mucosal folds. It was lined by stratified epithelium with goblet cells. In addition to club cells were observed in between the stratified epithelium. Scanning electron examination of the oesophageal epithelium of catfish demonstrated the presence of microvilli and fingerprint-like microridges in the superficial cell layer. The posterior part of the oesophagus of catfish was characterized by simple columnar mucus-secreting epithelium. The oesophagus of grass carp had shown the same structure along its entire length. It consisted of less folded mucosa than that observed in the oesophagus of catfish. The epithelium was characterized by the presence of taste buds. In conclusion, the present work revealed some differences in the structure of catfish oesophagus and grass carp oesophagus. These differences are related to type of food and feeding habits of each species. 1. Introduction Nile catfish (Clarias gariepinus) is one of the most abundant and widely distributed fish in the Nile River. Catfish has a wide geographical spread, a high growth rate, resistant to handling and stress, and well appreciated in a wide number of African countries. It is considered the third important commercial fish in Egypt after tilapia and bagrids [1, 2]. It can be recognized by its long dorsal and anal fins, which gives it a rather eel-like appearance. The catfish is carnivorous in type, where tilapias are its most preferred food item especially the young ones followed by insects, crustaceans, and mollusks, respectively [3]. The grass carp or white amur (Ctenopharyngodon idella) is a large cyprinid fish. They are native in large Asian rivers such as Amur River Basin in Russia and the West River in China [4]. It is a fast growing herbivorous fish; it usually feeds on grass or other aquatic vegetations and can be grown together with other fish species. The gastrointestinal tract of grass carp consisted of oesophagus, stomach, and intestine that ends at the anus. Food enters a short, often greatly distensible esophagus leading into a thick-walled stomach [5, 6]. The histological structure of the gastrointestinal tract of numerous fish species generally consists of mucosa, submucosa,
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