Abstract: This paper reports the histopathological changes of haemorrhagic mouth-opening disease of the eel, Anguilla japonica in China. Hyperaemia and haemorrhage were observed in tissues of the liver, spleen and kidney of the diseased fish. Bone tissues of the diseased fish were infiltrated with leucocytes. Pathological changes were also observed in organelles of the cells in the liver, spleen and kidney. Chronmatin argination , strange necleus, myolin-sheath-like saretures, autophagosomes and autophagolysosomes were observed in blood cells of haemopoietic tissues in the spleen and kidney, of periphery blood. The apoptotic-cell and apopotic-bidt like structures,incteased phogosomes in neighbouring cells were also observed in the cells of the spleen and kidney. Based on the filtration of leucocytes in the bone tissues and the atypia of some satructures in a parts of cells, it is suggested that the haemorrhagic mouth-opening disease of the eel is tending to pathological changes of a cancer.