Text Box: DISTINGUISH LEUKEMIA AND LEUKEMOID REACTION BY CLONAL ASSAY Lin Wen, Xiao Y Department of Pediatrics,Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China Objective: To verify whether the case that accord with the standard of leukemia FAB is a no clonal proliferation that is known as leukemoid reaction. Method: Restriction fragment length polymorphism (RFLP) of human androgen receptor gene (HUMARA) and phosphoglycerate kinase (PGK) at chromose. Results: 1of 4 patients who accord with the standard of leukemia FAB is a no clonal proliferation. He had not take chemotherapy and recovered perfectly after one month. Conclusion: Acute leukemia and leukemoid reaction have different natures. It is difficult to distinguish them only by morphologic and immunologic methods. Sometimes it results in erroneous diagnoses. So, it is necessary that every patients who were diagnosed the leukemia accept clonal assay routinely. 2378