Differentiation of the alimentary tract during larval development of asp (Aspius aspius L.) was followed using histological techniques. At hatching, the mouth cavity, pharynx, and oesophagus of the larvae were occluded. The intestine, in the form of a straight tube with undifferentiated cells, was resting on the yolk sac. Between days 3 and 5 post hatch, the intestine opened at both ends and lined with columnar epithelium. Signs of digestion and lipid absorption by enterocytes were observed on day 5, while protein absorption started on day 7 of the larval development. Goblet cells that produce acid mucins were detected among differentiating cells of the mouth cavity on the day of hatching. Intestinal mucous cells appeared on day 5 and began secreting neutral and acid mucins. The yolk sac was completely resorbed on day 11 post hatch. On day 21, the larvae measured, on the average, 17.23 mm in total length.

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