In this study the lead and cadmium concentrations in the liver, intestine, muscle and gonad of the shark Carcharhinus dussumieri and its parasites, Anthobothrium sp. and Paraorigmatobothrium sp. (Cestoda), were measured and compared. Tissue samples were collected from Iranian coastal waters of the Persian Gulf. After tissue preparation, the cadmium and lead concentrations were analysed using the Inductively Coupled Plasma technique. The results revealed that lead and cadmium concentrations in both parasite species were many times higher than in the host tissues. The results strongly support the view that helminth parasites are extremely sensitive early warning bioindicators, particularly in sensitive environments under threat but where pollution levels are presently low. They may also have a beneficial effect on the health of their hosts by acting as heavy metal filters.''