Human angiotensin converting enzymcC4CE) gene displays an insertion/deletion polymorphism in 16 intron, and three genotypes are determined by presence or absence of a 287-bp fragment of DNA; II, ID and DD genotype. DD genotype has been suggested as a risk factor of various cardiovascular diseases and chronic nephropathies such as IgA nephropathy and diabetic nephropathy. This study was designed to investigate if the ACE polymor-phism is related to the clinical and pathologic findings of minimal change nephrotic syndrome(MCNS) and focal segmental glomerulosclerosis(FSGS) in children. Ninety children with primary nephrotic syndrome(MCNS and steroid responsive nephrotic syndrome : 68 cases, FSGS; 22 cases) and 97 healthy normal controls were examined. The genotype for the polymorphism was determined by PCR method. The distribution of ACE genotypes in primary nephrotic syndrome(II 28.6%, ID 53.8%, DD 17.6%) was not different from that in controls(II 39.2%, ID 41.2%, DD 29.6%). The IJ genotype was more frequent in FSGS(II 64.7%, ID 23.5%, I)D 11.8%) than in MCNS and steroid responsive nephrotic syndrome(I 20.3%, ID 60.8%, DD 18.9%, p<0.03). The ACE genotypes were not associated either with frequency of relapse in MCNS or steroid responsive nephrotic syndrome or with presence of hypertension, responsiveness to steroid therapy and progression of renal dysfunction in FSGS. We concluded that deletion polymorphism of ACE gene is not associated with increased risk for renal progression in children with primary nephrotic syndrome.