The aim of the study was to study the distribution of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism, and its association with steroid responsiveness in children with idiopathic nephrotic syndrome (INS). One hundred twenty-five children with INS were classified into two groups: steroid-sensitive nephrotic syndrome (SSNS: n = 90) and steroid-resistant nephrotic syndrome (SRNS: n=35). The control group consisted of 150 unrelated healthy children. Genomic DNA was extracted from peripheral leucocytes by the standard salting-out method. ACE genotyping was performed and ACE genotypes DD, ID, and II were compared between different groups. The frequency distribution of the DD genotype was significantly increased in children with INS compared to control subjects (P = 0.0012) while the difference was not significant (P = 0.071) between SSNS and control subjects. The frequency distribution of the DD genotype was significantly high in the SRNS group compared to control subjects (P < 0.0001). The distribution of the DD genotype was high in SRNS compared to SSNS group patients (P = 0.016). In conclusion, the presence of the DD genotype may predict risk for steroid resistance in childhood INS.