AIM: To assess the absolute number of T-regulatory cells (Tregs; CD4+CD25+Foxp3+) in the peripheral blood of gastric and colorectal cancer patients. METHODS: We enrolled 70 cancer patients (33 gastric cancer, 37 colorectal cancer) and 17 healthy volunteers. The CD3+CD4+ lymphocytes and CD4+CD25+Foxp3+ Tregs in the peripheral blood were analyzed with flow cytometry. The absolute numbers of Tregs were calculated based on the CD4+CD25+Foxp3+ cells percent-age of CD3+CD4+ cells and the absolute numbers of CD3+CD4+ cells per microliter. RESULTS: The mean number of CD4+CD25+Foxp3+ cells per microliter in colorectal cancer patients was 15.7 (SD: 21.8), for gastric cancer patients 12.2 (SD: 14.3), and for controls 17.5 (SD: 11.4). The absolute number of Tregs was significantly lower in gastric cancer patients than in controls (P = 0.026). There was no statistically significant difference for gastric vs colorectal cancer or colorectal cancer vs controls. The absolute number of Tregs was also significantly depressed in N+ vs Ncancer patients [22.0 (27.7) vs 10.1 (9.0), P = 0.013], and in the subgroup of gastric cancer patients [30.3 (27.6) vs 9.6 (8.0), P = 0.003]. No statistical difference was observed in the proportion of Tregs in the CD4+ population between the groups. CONCLUSION: The absolute number of Tregs in peripheral blood of gastric cancer but not colorectal cancer patients was significantly decreased in comparison with that in healthy controls. AIM: To assess the absolute number of T-regulatory cells (Tregs; CD4 + CD25 + Foxp3 +) in the peripheral blood of gastric and colorectal cancer patients. METHODS: We enrolled 70 cancer patients (33 gastric cancer, 37 colorectal cancer) and 17 The volunteers’ healthy volunteers. The CD3 + CD4 + lymphocytes and CD4 + CD25 + Foxp3 + Tregs in the peripheral blood were analyzed with flow cytometry. The absolute numbers of Tregs were calculated based on the CD4 + CD25 + Foxp3 + cells percent- age of CD3 + CD4 + cells and the absolute numbers of CD3 + CD4 + cells per microliter. RESULTS: The mean number of CD4 + CD25 + Foxp3 + cells per microliter in colorectal cancer patients was 15.7 (SD: 21.8), for gastric cancer patients 12.2 The absolute number of Tregs was significantly lower in gastric cancer patients than in controls (P = 0.026). There was no statistically significant difference for gastric vs colorectal cancer or colorectal cancer vs controls. The absolute number of Tregs was significantly lower in gastric cancer patients than in controls Tregs was also si gnificantly depressed in N + vs Ncancer patients [22.0 (27.7) vs 10.1 (9.0), P = 0.013], and in the subgroup of gastric cancer patients [30.3 (27.6) vs 9.6 (8.0), P = 0.003] was observed in the proportion of Tregs in the CD4 + population between the groups. CONCLUSION: The absolute number of Tregs in peripheral blood of gastric cancer but not colorectal cancer patients was significantly decreased in comparison with that in healthy controls.