Immunohistochemical and ultrastuructural experiments were conducted to find out heavy metal accumulation in the intestine of an Antarctic gastropod Nacella concinna. According to the immunohistochemical experiment the apical cytoplasm of the intestinal epithelium showed positive reactions to anti-MT (metallothionein), indicating the presence of MT, a metal-binding protein involved in metal detoxifying process. In the transmission electron microscopic observations, the epithelial cells of the intestine exposed to Cd for over three hours showed irregular nuclear membranes, secretory granules, and probable metal granules. According to the SEM-EDS experiments on the intestine, concentration of Pb in the apical epithelium was in inverse proportion to that in the intestinal lumen. After exposing to Cd for over three days, S was rapidly reduced. Ca and Zn wererapidly increased after exposure to Cd. These elements are supposed to be concerned with the MT-reaction in the intestine. Taken together, these data suggest that N. concinna could be used as a potential biomarker species.