The aquatic macrophyte Azolla mexicana was studied to determine if it could indicate toxicity and bioavailability of cadmium, copper, and zinc in sediments. Plants were exposed to metal-fortified artificial sediment and to natural sediment contaminated with tailings from a Superfund site near Deer Lodge, Montana. Dry weights (mass) of biomass were used to determine effects of the metal concentrations and tissue metals were measured to determine metal uptake from the sediments. Plants exposed to artificial sediments fortified with cadmium and copper showed the greatest reduction in dry mass while zinc showed the least. And, plants exposed to copper singly in artificial sediments lost both zinc and cadmium from their tissues. Plants exposed to metal-contaminated natural sediment developed necrotic and chlorotic tissue within 24 hours in 75% and 100% dilutions but significant effects (P<0.0001) using dry mass were found as low as 3.13%.