Surgery is the best treatment for primary GIST and may be curative, but resection extension/completeness impact on the prognosis remains controversial. The authors aim was to evaluate the clinicopathological (CP) parameters and surgical margins status influence on GIST patients' outcome. The study evaluated 113 consecutive patients with sporadic GIST; the influence of CP parameters on recurrence-free survival (RFS) and disease-specific survival (DSS) was determined by univariate analysis (UA) and multivariate analysis (MA). Of 104 cases, macroscopically complete resection was achieved in 96: R0 surgical margin status in 78 and R1 in 18. Recurrence rates (12.5%) were significantly lower in R0 (9.0%) than in R1 (27.8%). Tumor > 10 cm, mitotic count > 5/50 high power field (HPF), and high-risk GIST predicted poor RFS and DSS (UA). Disease-specific survival was significantly shorter after macroscopic incomplete (R2) resection, for mixed cellular morphology, and in tumors with necrosis (UA). High-risk GIST (p = 0.016) and R2 resection (p = 0.013) predicted poor DSS of patients (MA). High risk and positive macroscopic surgical margin status are parameters associated with poor disease-specific survival in GIST patients.