Effects of oral administration of lead and cadmium on structure and function of trout intestine were investigated inSalmo gairdneri.Fish were fed either cadmium (5 mg kg*1fish per day) or lead (10 mg kg−1fish p er day) and sacrificed after a 15 or 30 day treatment.Levels of cadmium and lead in kidney, liver and spleen were significantly increased by the 15th day of treatment.Following both cadmium and lead treatment, morphological observations showed an increased mucous cell activity, a disruption of intestinal brush border and an increased renewal rate of absorptive cells.Influx (Jms), outflux(Jsm)of chlorine and sodium ion and net fluxes were measured on perfused intestinal segments and ouabain‐sensitive sodium, potassium‐ATPase (Na, K‐ATPase) activity was determined on intestinal scrapings. Cadmium did not alter either sodium chlorine transepithelial fluxes or sodium, potassium‐ATPase activity, but lead did. In the middle intestine, lead modified significantly transepithelial sodium and chlorine fluxes (JmsNa: 3.21 ± 0.34 to 1.79 ± 0.29 and JmsCl: 3.32 ± 0.34 to 1.86 ± 0.22μmol h−1cm−2,n = 6)after 30‐day diet.Jnetremain unchanged and Na, K‐ATPase activity decreased. In the posterior intestine, lead altered onlyJmsNa (1.95 ± 0.31 to 0.37 ± 0.09μmol h−1cm−2) andJmsCl. ConsequentlyJneswere also decreased.So, although both cadmium and lead induce morphological disorders in the middle and in the posterior intestine of the trout, they have different effects on the