The morphology and cytochemistry of melano-macrophage centers (MMCs) in spleen and kidney of eel (Anguilla anguilla) were assessed by employing technologies of histochemistry and transmission electron microscopy. The results showed that there were MMCs both in spleen and kidney with round, oval or irregular shape; the majority of MMCs in spleen distributed regularly around blood vessel, on the contrary, MMCs in kidney did not follow the rule; the MMCs both in spleen and kidney were contained with haemosiderin, melanin and lipofuscin, while, haemosiderin dominated in the former and melanin and lipofuscin did in the latter. Ultrastructural observations revealed that there were granular pigments and cellular debrises in MMCs of spleen. It seemed that MMCs in spleen and kidney undertook different function inferred from the experiments.