PURPOSE: A gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract. There are only few reports in the literature describing colorectal GISTs. The aim of this study was to evaluate the clinicopathologic features of colorectal GISTs and to verify prognostic factors. METHODS: We reviewed 14 patients diagnosed as having primary colorectal GISTs between 1992 and 2003. Clinicopathologic variables and immunohistochemical expressions were analyzed. The diagnostic criteria and grading system for the GISTs were based on the proposal by the National Institutes of Health in April 2001. The median follow-up period was 27 (1~137) months. RESULTS: The male-to-female ratio was 9 : 5, and the mean age was 61 (37~76) years. The primary location was the rectum (11 cases, 78.6%). The mean tumor size was 7.7 (1.5~17) cm, and the mean number of mitoses was 33.4 (1~150) per 50 HPF. Of the 14 patients, 10 patients (71.4%) were regarded as a high-risk group and four patients as an intermediate-risk group. KIT protein and CD34 were expressed in 92.9% and 78.6% of the cases, respectively. The patients were subclassified based on immunohistochemical expressions as an uncommitted type in 11 cases (78.6%), a combined type in 2 cases (14.3%), and a myoid type in 1 (7.1%) case. Recurrence occured in three patients (21.4%) who were in the high-risk group. CONCLUSIONS: Colorectal GISTs occurred predominantly in the rectum and tended to be classified as high risk, which was the most important risk factor for recurrence. Accurate diagnosis and grading are important for adequate treatment and accurate prognosis.