The aim of this study was to investigate the prevalence of interleukin (IL)-17-producing CD4+ T cells (Th17) and regulatory T (Treg) cells in children with primary nephrotic syndrome. The study cohort consisted of 62 children who were randomly divided into control, primary nephrotic syndrome, and isolated hematuria groups. Flow cytometric analysis revealed the presence of Th17 cells in the peripheral blood mononuclear cells (PBMCs) of 35 children and Tregs in the PBMCs of all children. In addition, mRNA expression of Th17-related factors [IL-17, -23p19 and retinoid orphan nuclear receptor (RORc)] and the concentration of plasma inflammatory mediators such as IL-6 and IL-1beta were consistently detected in all children. Protein expression of IL-17 and transforming growth factor-beta1 were also detected in renal biopsy tissue and compared between different groups. Patients with PNS were found to have an increased number of Th17 cells and decreased numbers of Tregs in their PBMCs, and there was significant difference in the prevalence of Th17 and Tregs between the patients with PNS and those with isolated hematuria. Our data show that among our study cohort, there was a dynamic equilibrium between Th17 and Treg cells in children with PNS following the development of PNS with apparent renal tubular epithelial cell and interstitium lesions. The dynamic interaction between Th17 and Treg cells may be important in the development of PNS.