BACKGROUND AND AIM CD133 expression in cancer cells has been recognised as a putative cancer stem cell (CSC) marker in epithelial malignancies. CD133 expression was evaluated in gastric cancer and the clinical impact of CD133-positive gastric cancer was clarified. PATIENTS AND METHODS Ninety-seven gastric cancer patients who received curative gastrectomy were enrolled. CD133 expression in cancerous tissue was evaluated by immunohistochemistry. RESULTS CD133 expression positively correlated with tumour extension and the degree of nodal involvement. CD133 expression significantly affected patient postoperative outcome. Multivariate analysis revealed CD133 positivity as an independent prognostic factor superior to the depth of invasion and similar to nodal involvement in gastric cancer (p<0.05). CONCLUSION Even slight CD133 expression in gastric cancer patients may be a useful prognostic marker via CSC. Further examination of CD133 with respect to CSC markers can enable prediction of the recurrence risk of gastric cancer.