To study the toxic effect of a heavy metal on the occurrence of melano macrophage centres (MMC) of liver, spleen and kidney. Tilapia mossambica were exposed to median lethal concentration of cadmium chloride for 120 hours. Routine histological method was adopted to prepare the tissue sections and to identify the pigments viz: hemosiderin and melanin. The average number and size of melano macrophage centres (MMC) were significantly increased compared with the control. It is evident in the present study that in the MMC of all three tissues examined lipofuscin is absent.