Background and Objective: Non-Hodgkin's lymphoma (NHL) is a malignant disease originating from immune system. Studies of the possible relationship between NHL and Immune suppression status are of great concern. Regulatory T cell (Treg) is a subtype of T cells that exert an immunosuppressive function. However, the relationship between Treg and lymphoma Is controversial. The study was to detect peripheral blood levels of Treg in patients with NHL and healthy adults, and to explore the possible relationship between peripheral blood Treg level and NHL. Methods: By using flow cytometry with surface staining fluorochrome-conjugated antibodies for CD4, CD25, CD127, the percentages of CD4+CD25highCD127low Treg in peripheral blood of 31 healthy adults and 99 newly diagnosed NHL patients, hospitalized In Sun Yet-sen University Cancer Center from December 2006 to March 2008, were detected and analyzed. Results: The average peripheral blood CD4+CD25highCD127low Treg levels were 8.07±1.90 and 11.20±4.40 In healthy adults and newly diagnosed NHL patients, respectively. The difference of peripheral blood Treg levels between them was statistically significant (P<0.001,95% CI: 2.02-4.23). The peripheral blood level of Treg was significantly higher in the male NHL patients than in the female patients(P=0.030,95% CI: 0.19-3.77). Patients with bad habits (smoking, addict to drink, or both) had significantly higher peripheral blood Treg level than patients without bad habits (P=0.045,95%CI: 0.04-3.84). It was no significant relation between peripheral blood Treg level and age, stage, I PI, B symptom, bulky disease, LDH level, pathologic subtype, short term response, HBV infection, and so on. The analysis in diffuse large B-cell lymphoma (DLBCL) subtype showed the same results. Conclusions: Newly diagnosed NHL patients are in an immunosuppressive statue. Patients with bad habits (smoking, addict to drink, or both) have higher peripheral blood Treg level. Peripheral blood Treg level is irrelevant to the status of disease.