Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by various immunological abnormalities. Regulatory T cells (Tregs) CD4+CD25+ play an important role in maintaining tolerance to self-antigens controlling occurrence of autoimmune diseases. It has been shown that the transcription factor forkhead box P3 (FoxP3) is specifically expressed on CD4+CD25+T cells. FoxP3 has been described as the master control gene for the development and function of Tregs. A decrease in the number of CD4+CD25highFoxP3+ regulatory T cells can play a key role in the loss of tolerance to self antigens. The study was designed to assess expression levels of FoxP3 in peripheral CD4+CD25+ regulatory T cells in patients with SLE and to evaluate the level of some cytokines that are implicated in the extent of the disease activity. The study was carried out on 30 SLE patients, they were 27 females and 3 males, 10 age and sex matched healthy volunteers were studied as a control group. They were divided into two groups: group I: had active disease (12 patients) and group II: had inactive disease (18 patients) according to Systemic Lupus Erythematosus Disease Activity Index. All individual were subjected to CBC, ESR, s.creatinine, RF, CRP, C3, ANA, anti ds-DNA and flowcytometeric assay of CD4+CD25+ (Tregs) and FoxP3 for patients and controls. Quantitative determination of serum interleukin 10 (IL-10) and transforming growth factor-beta1 (TGF-beta1) concentrations in serum samples by ELISA technique. The results revealed a significant decrease of CD4+CD25high cells in peripheral blood in active lupus patients when compared with patients with inactive lupus and those in healthy controls. Intriguingly, the percentage level of FoxP3 on CD4+CD25high cells was significantly decreased in SLE patients with active disease (2.9 +/- 1.05) when compared with those with inactive SLE (3.5 +/- 0.8) and control groups (4.7 +/- 1.2) (P < 0.05). As regard cytokines levels; the level of IL-10 was significantly increased in patients with active and inactive disease (158.8 +/- 50.8, 82.8 +/- 14.08 respectively) when compared with the control group (P < 0.001). While, the level of TGF-beta1 was significantly decreased in patients with active and inactive disease (22.5 +/- 7.03, 29.07 +/- 10.14 respectively), when compared with the control group (P < 0.05). Our data revealed impaired production of Tregs in SLE patients, which may play a reciprocal role with some cytokines to affect the activity of the disease. Tregs cells should be the target to determine the clinical effectiveness of novel therapy to modulate Tregs in vivo besides the conventional treatments.