Information is provided regarding thè attachment mechanism and damage Leptorhynchoides plagicephalus (Acanthoce-phala) causes to digestive tract of Acipenser naccarii. Seventeen out of twenty-one A. naccavii specimens examined proved to be infected by L. plagicephalus. The parasite attaches itself to thè depth of intestinal folds by means of its pro-boscis causing extensive lesions which can become thè site of secondary infec-tions brought about by pathogenic microorganisms such as bacteria. The L. plagicephalus proboscis rarely passes beyond thè compact layer of lamina propria ; although it occasionally reaches thè circular muscle layer of intestinal wall. As a response to parasitic presence in thè attachment zone, thè host tissue produces a fibrous thickening and shows a marked infiltration of leucocytes, mainly lymphocytes and eosinophilic granulocytes.