[Abstract] Objective To explore the prognostic significance of P53、D13S25、ATM gene deletion in patients with chronic lymphocytic leukemia(CLL)．Methods Interphase fluorescence in situ hybridization (FISH) were used to detect P53、D13S25、ATM gene deletion in 75 patients．P53、D13S25、ATM gene deletion and their association with efficacy of Fludarabine and Cyclophosphamide were analyzed. Results Out of the75 CLL patients，The total incidence of these karyotypic abnormalities is 26.3% by FISH. 。p53 gene deletion was found in 16（21.3%）cases,D13S25 gene deletion in 22（29.3%）cases, ATM gene deletion in 12（16%）cases,Complex karyotype in 6（8%）cases.Among 32 patients who received FC Chemotherapy,none of the 7 cases with p53 gene deletion achieved complete response,while 12 of 25(48.0%) cases without the gene deletion achieved CR(P=0.029); 3 of the 9 (33.3%) cases with D13S25 gene deletion achieved complete response,while 9 of 23(39.1%)cases without the gene deletion achieved CR(P=1.000); none of the 8 cases with ATM gene deletion achieved complete response,while 12 of 24(50%) cases without the gene deletion achieved CR (P=0.014). There was no signifieant differences of P53、D13S25、ATM gene deletion rates in sex，age， peripheral lymphocyte count，and the levels of LDH，32-MG，and Binet stages. Conclusion FISH can effectly detect the chromosomal abnormalities of CLL. CLL patients with p53 and／or ATM gene deletion had poor therapeutic effect，and hence poor prognosis,while who with D13S25 gene deletion had better therapeutic effect. These gene deletions have important prognostic value.