Objective To evaluate preoperative endoscopic ultrasonography(EUS)for diagnosis and invasive risk assessment of gastric gastrointestinal stromal tumors(GISTs). Methods A total of 248 patients diagnosed as having gastric GISTs based on preoperative EUS and with established pathologic results at our institution were recruited to the study. The coincidence rates for gastric GISTs between preoperative EUS and pathologic results were calculated. Univariate and multivariate analyses were used to explore the possible predictors for the coincidence rates. EUS features were compared according to histological risk classification of very low/low risk malignant potential or intermediate/high risk malignant potential. Results The overall coincidence rate for gastric GISTs between EUS and pathologic results was 67.7%(168/248). Univariate analysis showed that tumor diameter, mucosal bridge, heterogeneity, and calcification were significantly correlated with the coincidence rate for gastric GISTs between preoperative EUS and pathologic results. Multivariate analysis indicated that heterogeneity (OR=2.53, 95%CI: 1.23-5.18, P=0.011) and calcification(OR=2.25, 95%CI: 1.34-6.56, P=0.045) were the independent factors for the coincidence rate. A total of 168 patients were divided into four groups according to histological risk: very low risk(n=63), low risk(n=62), intermediate risk(n=26), and high risk(n=17). Gastric GISTs with heterogeneity, mucosal ulceration, and calcification on EUS suggested higher risk GISTs. Multivariate analysis indicated that only tumor diameter(P<0.000 1)could predict malignant potential of gastric GISTs. Conclusion Preoperative EUS plays an role in diagnosing and evaluating of invasive risk for gastric GISTs, which might aid the clinical management of gastric GISTs. Key words: Risk assessment; Mesenchymoma; Endosonography