In the present study the action of cadmium, a well known environmental pollutant, on the salt absorptive function of the eel, Anguilla anguilla, intestine was evaluated by estimating the rate of net Cl− absorption expressed as short circuit current (Isc, μA cm−2). In tissues mounted on Ussing chamber, Isc and transepithelial potential difference (Vt, mV) responded in a concentration dependent manner to the addition of CdCl2 to the serosal or mucosal bathing solutions. The dose response curve indicated that the maximal inhibition of Isc and Vt (90% inhibition) after 1 h of incubation was obtained at a concentration of 100 μM from the serosal side and 5 mM from the mucosal one. To understand the nature of Isc inhibition induced by cadmium, the response of electrical parameters to the heavy metal exposure was examined in tissues exposed to different substances known to block Cl− transport at different cellular levels. Hence, bumetanide, which is known to inhibit Cl− transport by blocking the luminal Na+–K+–2Cl− cotransporter and Cl−-conductive channels at the basolateral membrane of the enterocyte, added to the mucosal (10 μM) or the serosal solution (100 μM), abolished the response of Isc and Vt to CdCl2 treatment. Similar results were obtained when tissues were pre-treated with ouabain (serosal, 100 μM) or when Na+ or Cl− were omitted from the bathing media. Furthermore, cadmium alters the permselectivity of the tight junctions since the magnitude of the diffusion potential evoked by an imposed serosa–mucosa NaCl gradient (2:1) was strongly reduced by addition of CdCl2 to either serosal or mucosal solution. Microelectrode experiments point to a relative impermeability of the luminal membrane to the heavy metal since the luminal membrane potential (Vm) remains unchanged during perfusion with CdCl2. The results suggest that cadmium acts on the transport process responsible for Cl−-absorption in eel intestine. Therefore, one of the factors contributing to the toxic effect of cadmium on fish could be related to the ion-balance disturbances of body fluids subsequent to the altered osmoregulatory function of the intestine in marine teleosts.