Abstract: Objective:To analyze the association of thrombocytosis with the prognosis of patients with gastric cancer. Methods:The clinical materials of 782 patients with gastric cancer who underwent initial surgery in our hospital between January 1995 and December 1999 were retrospectively analyzed. Kaplan- Meier and Log-Rank test were used to analyze the data. Prognostic factors were analyzed by multivariate Cox proportional hazards model. Results: Thrombocytosis oc curred in 11.4% (87/782 ) patients. The platelet level was not significantly different among patients of different gender, tumor stage, and histological differentiation (P>0.05). However, a significant difference was observed in the platelet level among patients with different age and surgical approach ( P<0.05). The 1-, 3-, and 5-year survival rates were 75.0% ,40.1% and 28.9% in patients without thrombocytosis and52.8%,16.9%, and13.5% in patients with thrombocytosis (P=0.002 ). Univari-ate analysis showed that histological differentiation, pathological stage, surgical approach and thrombocytosis significantly affected the survival of patients. While age and gender had no significant impact on patient survival. Multivariate analysis showed that pathological stage, surgical approach, and thrombocytosis were independent prognostic factors for gastric can-cer. The relative risk of death of patients with thrombocytosis was elevated by 1.454 times (RR=1.454 , 95% CI: 1.135 ～1.861 , P=0.005 ). Conclusion:Thrombocytosis is an independent prognostic indicator for the survival of initially treated pa-tients with gastric cancer.