Background. The renin-angiotensin system (RAS) has been considered to be responsible for the pathogenesis or progression of many diseases which may or may not be related to kidney. Genetic polymorphisms of the various components of the RAS have been associated with differences in the clinical course of several disease states in adults and children. Objectives. The purpose of our study was to investigate RAS gene polymorphisms in patients with steroid resistant primary focal segmental glomerulosclerosis (FSGS) and nephrotic syndrome responding to steroid therapy. Furthermore, we aimed to investigate whether there was an association between polymorphic alleles and responses to steroid therapy, the degree of renal dysfunction, and prevalence of end-stage renal disease (ESRD). Material and methods. One hundred and fifty-eight children with the diagnosis of nephrotic syndrome were recruited from the Nephrology unit in the Department of Paediatrics of Ege University. Forty-nine of them were classified as renal biopsy-proven FSGS and 102 patients were considered to have response to steroid treatment. Renal functional impairment was detected in 19 subjects with FSGS and end-stage renal insufficiency in 13 patients. The control group consisted of 287 healthy adult subjects. Angiotensin-converting enzyme (ACE), angiotensin II type 1 receptor (AT1R) and angiotensinogen (AGT) gene polymorphisms were determined by the polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) technique. Statistical significance was regarded as p<0.05. Results. There were no statistically significant differences for the C allele of AT1R or the T allele of AGT genes between the children with nephrotic syndrome and control group, but on the other hand statistically significant differences were detected for D allele of ACE gene. There was no significant relationship detected between the D allele of ACE, the C allele of AT1R or the T allele of AGT genes and response to steroid therapy, extent of renal dysfunction and the progression to ESRD. However, there was a significant relationship between T allele of AGT gene and resistance to steroid treatment (OR; 4,837, 95% CI; 1,723—13,577, p=0.01), renal dysfunction (OR; 3,189, 95% CI; 0,999—10,182, p=0.041) and progression to ESRD (OR; 3,852, 95% CI; 1,057—14,040, p=0.03). Conclusion. In this study, the angiotensino gene -235T allele was found to be related with steroid resistance, renal dysfunction and progression of ESRD in nephrotic syndrome.