Endoscopic submucosal dissection (ESD) is commonly used for radical resection of gastric adenoma and mucosal cancer, but there is about 30% of discrepancy rate between the histology of the endoscopic biopsy and that of the resected specimen obtained from the same lesion by ESD. The aim of this study was to clarify the clinical significance of IL-6, VEGF, CRP before ESD. We investigated the correlation between serum IL-6, VEGF, CRP level and discrepancy rate of gastric neoplastic lesions (10 low-grade dysplasias, 18 high-grade dysplasias, and 25 early gastic cancers). Serum levels of IL-6 in gastric adenoma and mucosal cancer patients were significantly higher than in healthy controls (p<0.05). Especially, serum IL-6 level of high-grade dysplasia patient was significantly higher than low-grade dysplasia and mucosal cancer patients, and the positive rate, sensitivity, and negative predictive value of serum IL-6 levels were higher in high-grade dysplasia patient compared to low-grade dysplasia patient and mucosal cancer patient. Serum levels of VEGF in patients with gastric adenoma and mucosal cancer were significantly higher than healthy controls (p<0.01). Serum levels of CRP in patients with mucosal cancer were significantly higher than in the controls (p<0.05), and the positive rate, sensitivity, and positive predictive value of serum CRP levels were higher in high-grade dysplasia and mucosal cancer patients compared to low-grade dysplasia patient. Serum levels of IL-6, VEGF, and CRP in patients with gastric neoplastic lesions were significantly higher than healthy controls, especially, serum IL-6 level of high grade dysplasia patient was significantly higher than low-grade dysplasia and mucosal cancer patients.