Background: Angiotensin-converting enzyme gene (ACE; OMIM: 106180) is located on 17q23.3 chromosomal site with functional insertion/deletion polymorphism. The frequency of cases with DD genotype is higher than that of genotypes ID and II. In this study, the association between the gene and severe lymphoblastic leukemia was investigated. 
Materials and Methods: This case-control study was conducted on 50 patients with severe lymphoblastic leukemia. ACE I/D polymorphism was detected by the Gap-PCR technique. PCR products were isolated and measured by electrophoresis on 1% agarose gel. The Insertion (I) allele was observed in the band of 478 bps and the Deletion allele (D) in the 191 bps band. 
Results: It was estimated that the absence of ID genotype is related to the probability of developing severe lymphoblastic leukemia. In addition, DD and II genotypes had a p-value greater than 0.05 and the hypothesis of their association with brain invasion was rejected.
Discussion and Conclusion: With respect to the results, it should be noted that these findings are the first report of the association between ACE I/D polymorphism and severe leukemia lymphoblastic. Further studies are needed to confirm these findings.