Background: One of the most common types of gastrointestinal neoplasms is a GIST (gastrointestinal stromal tumourKi67 is a proliferation marker that can detect all but G0 proliferating cells. Objective: To evaluate Ki67 expression in GIST and its correlation with the clinicopathologic parameters including survival using immunohistochemical method. Patients and Methods:  In this study, Ki67 immunohistochemistry was performed on sections cut from 56 formalin-fixed, paraffin-embedded GIST. Diagnosis of GIST was confirmed by positive expression of C-kit in all cases except 5 negative cases that were positive for PDGFRA. Clinical data included age, gender, tumour location (gastrointestinal and extra gastrointestinal), tumour size, lymph node status, presence of distant metastasis, and patient status. The assessed pathological parameters included mitotic count, cell type (spindle, mixed spindle and epithelioid, epithelioid) and necrosis. Cases are divided into very low, low, moderate and high-risk groups according to National institute of health and 2006 risk stratification. Results: Ki67 expression ranged between 0.5-6.6 % with a median of 3 % and a mean±SD of 3.08±1.77 %. 60.7% had low Ki67 labelling index (LI) (below the median, ≤3%), 39.3% had high Ki67 LI (above the median ≥3%). Ki67 LI was significantly correlated to mitosis (P=0.010), 2006 risk stratification (P value=0.027) and with young patients (P=0.019). However, it has no correlation with the overall survival and rest of clinicopathological parameters. Conclusion: Ki67 could be included in risk stratification of GIST since its expression is correlated with GIST risk stratification.