Heavy metals impair the aquaculture of shrimps and the quality of shrimp products. Some heavy metals occur in high amounts particularly in the hepatopancreas and the antennal gland. This study was performed in order to determine whether copper, iron, and lead are accumulated in the hepatopancreas and the antennal gland extensions running along the hepatopancreas. Furthermore, damages of these metals and cadmium to the hepatopancreas cells were investigated. According to its commercial significance the giant tiger prawn, Penaeus monodon, was chosen as test species. Postlarvae of Penaeus monodon were exposed for 10 days to water contaminated with either 1 mg/l (1 ppm) copper, iron, lead, or cadmium. The animals (6 to 7 per treatment) were kept in 20 l fiberglass tanks. Every second day the water was completely changed and the metals were again added to a calculated final concentration of 1 mg/l. After 5 and 10 days samples were taken for light and electron microscopy. Fixation was carried out due to routine procedures. The accumulation of copper, iron, and lead in the tissues was investigated by means of histochemistry, and the metal-related ultrastructural alterations by electron microscopy. In the case of cadmium only the cytopathological signs were recorded.