Previous studies have reported that preoperative neutrophil-to-lymphocyte (NLR) and platelet-to-lymphocyte ratios were prognostic for various types of cancers.The aim of this study was to investigate the predictive utilities of preoperative peripheral blood counts in patients with gastrointestinal stromal tumors (GISTs).We enrolled 510 consecutive,previously untreated patients who underwent surgery for primary,localized GISTs.The relationship between recurrence-free survival and outcome variables was assessed by univariate and multivariate analyses,while the clinicopathologic relevance of NLR was determined using the Chi-square test.A preoperative NLR ≥2 was associated with poor prognosis in patients undergoing surgeries for primary,localized GISTs.It was an independent predictor only in patients classified as National Institutes of Health high risk but not in the entire population.Preoperative NLR is a feasible and reproducible peripheral biomarker that helps identify patients for intensive adjuvant therapy and frequent surveillance.