There are limited clinical investigations identifying the percentage of T helper 1 (Th1) and T regulatory (Treg) cells in stable as well as rejected kidney allografts, a concept which needs to be more studied. The aim of our study was to compare the percentage of CD4+ IFN-γ+ cells, the number of IFN-γ secreting cells and the amount of FoxP3 expression in patients with or without stable graft function, to determine the roles of these immunological factors in stable and rejected renal allografts. In this prospective study, 3 months after transplantation 30 patients who received renal transplants from unrelated living donors were enrolled and divided into two groups, 20 patients with stable graft function and 10 patients with biopsy proven acute rejection. The percentage of Th1 CD4+ IFN-γ+ cells was determined on PBMC by flow cytometry and the number of IFN-γ secreting cells by ELISPOT method. Furthermore, FoxP3 expression of PBMCs was measured by Real Time PCR method. The results of these assessments in both groups were statistically analyzed by SPSS 14.0. Our results showed that the percentage of Th1 CD4+ IFN-γ+ cells and the number of IFN-γ secreting cells were significantly higher in the patients with acute rejection in comparison to the stable graft function group (p<0.001). In addition, the level of FoxP3 gene expression was higher in the group with stable graft compared to the acute rejection group. The higher percentage of CD4+ IFN-γ+Th1 subset and number of IFN-γ secreting cells and also the lower expression of Foxp3 could prone the patients to acute rejection episode post transplantation. By these preliminary data, it is suggested that monitoring of Th1 cells post transplantation, as an immunologic marker could predict the possibility of rejection episodes.