The present study analyses two cases with acute immature eosinophilic leukemia. The clinical, physical, laboratory and pathologic materials are discussed. There is an abnormal number of immature eosinophilic calls in the blood and bone marrow, usually accompanied by anemia and thrombocytopenia. Especially the ultrastructural features include abnormal granules, asynchronous maturation of the nucleus and cytoplasm, dilated endoplasmic reticulum and more conspicuous nueleoli. Differential count was more precise under electron microscope than under light microscope. These findings may be helpful for differential diagnosis and classification.