Regulatory T cells (Tregs) play a central role in protecting the host from autoimmune diseases. However, Tregs also pose a major problem to anti-tumor immunity. The expansion and accumulation of these immunosuppressive cells correlate with advanced tumor growth and predict poor disease prognosis. The study aims at evaluation of the clinical role of regulatory T cells in B-cell Non-Hodgkin's lymphoma. The study was carried out on 45 de novo patients with B- NHL, they included 26 males and 19 females and 20 apparently healthy age-matched as control. Diagnosis of lymphoma was done by lymph node biopsy, 15 patients had diffuse large B cell lymphoma (DLBCL), 9 follicular lymphoma (FL), 8 small cell lymphocytic lymphoma (SCLL), 7 marginal zone lymphoma (MZL) and 6 had mantle cell lymphoma (MCL). Tregs (CD4+CD25+ FoxP+3) were analyzed by Flowcytometry. The mean percent was 10.9 +/- 1.6% in diffuse large B cell lymphoma, 12.4 +/- 1.4% in follicular lymphoma, 13.7 +/- 2.4% in small cell lymphocytic lymphoma, 11.9 +/- 1.9% in marginal zone lymphoma and 13.5 +/- 1.35% in mantle cell lymphoma as compared to 5.9 +/- 0.96% in controls with a significant increase in the patients in relation to control group. Tregs was significantly increased in advanced stages of the disease, in bone marrow infiltration and in patients with increased LDH level. In conclusion, Tregs may play a role in modifying immune responses in patients with lymphomas and may be useful in immunotherapy and new anti-lymphoma strategies involving depletion of Tregs.