The marine harpacticoid copepods Tigriopus brevicornis were collected along the French Atlantic Coast (Loire Atlantique) and subsequently exposed to different lethal and sublethal concentrations of various metals (copper, zinc, nickel, cadmium, silver and mercury) for varying lengths of time. Ultrastructural investigations of control and experimentally exposed copepods were performed to investigate the intracellular localization of metals using transmission electronic microscopy (TEM). Copepod digestive epithelium cells as well as the cuticular integument were found to be the major metal storage tissues. Different types of metal-containing granules were found in both metal-exposed copepods and the controls: (1) within lysosomes, (2) in intracellular calcospherites and (3) in extracellular tiny granules. The elemental composition of the granules was determined on ultrathin sections by means of energy dispersive X-ray spectroscopy (EDS). The results were interpreted by considering previous data in order to understand how Tigriopus brevicornis copes with the presence of metals in its environment.