AIM: To investigate the prognostic significance of perioperative leukopenia in patients with resected gastric cancer.METHODS: A total of 614 eligible gastric cancer patients who underwent curative D2 gastrectomy and adjuvant chemotherapy were enrolled in this study. The relationship between pre- and postoperative hematologic parameters and overall survival was assessed statistically, adjusted for known prognostic factors.RESULTS: The mean white blood cell count(WBC) significantly decreased after surgery, and 107/614(17.4%) patients developed p-leukopenia, which was defined as a preoperative WBC ≥ 4.0 × 109/L and postoperative WBC < 4.0 × 109/L, with an absolute decrease ≥ 0.5 × 109/L. The neutrophil count decreased significantly more than the lymphocyte count. P-leukopenia significantly correlated with poor tumor differentiation and preoperative WBC. A higher preoperative WBC and p-leukopenia were independent negative prognostic factors for survival [hazard ratio(HR) = 1.602, 95% confidence interval(CI): 1.185-2.165; P = 0.002, and HR = 1.478, 95%CI: 1.149-1.902; P = 0.002, respectively] after adjusting for histology, Borrmann type, p TNM stage, vascular or neural invasion, gastrectomy method, resection margins, chemotherapy regimens, and preoperative WBC count. The patients with both higher preoperative WBC and p- leukopenia had a worse prognosis compared to those with lower baseline WBC and no p-leukopenia(27.5 mo vs 57.3 mo, P < 0.001). CONCLUSION: Preoperative leukocytosis alone or in combination with postoperative leukopenia could be independent prognostic factors for survival in patients with resectable gastric cancer. AIM: To investigate the prognostic significance of perioperative leukopenia in patients with resected gastric cancer. METHODS: A total of 614 eligible gastric cancer patients who underwent curative D2 gastrectomy and adjuvant chemotherapy were enrolled in this study. The relationship between pre- and postoperative hematologic parameters and overall survival was assessed statistically, adjusted for known prognostic factors. RESULTS: The mean white blood cell count (WBC) significantly decreased after surgery, and 107/614 (17.4%) patients developed p-leukopenia, which was defined as a preoperative WBC ≥ 4.0 × 109 / L and postoperative WBC <4.0 × 109 / L with an absolute decrease ≥ 0.5 × 109 / L. The neutrophil count was significantly more than the lymphocyte count. P-leukopenia significantly correlated with poor tumor differentiation and preoperative WBC . A higher preoperative WBC and p-leukopenia were independent negative prognostic factors for survival [hazard ratio (HR) = 1.602, 95 % confidence interval (CI): 1.185-2.165; P = 0.002, and HR = 1.478, 95% CI: 1.149-1.902; P = 0.002, respectively] after adjusting for histology, Borrmann type, p TNM stage, vascular or neural invasion , gastrectomy method, resection margins, chemotherapy regimens, and preoperative WBC count. The patients with both higher preoperative WBC and p-leukopenia had a worse prognosis than those with lower baseline WBC and no p-leukopenia (27.5 mo vs 57.3 mo, P <0.001). CONCLUSION: Preoperative leukocytosis alone or in combination with postoperative leukopenia could be independent prognostic factors for survival in patients with resectable gastric cancer.