Distinguishing primary ovarian cancer from metastatic ovarian cancer may be difficult. The treatment and prognosis of primary ovarian cancer and metastatic ovarian cancer are distinctly different; therefore, it is important to distinguish between these two types of cancer. We report two cases of Krukenberg tumor that presented challenges in establishing a preoperative diagnosis. Bilateral ovarian tumors with pathological findings of signet ring cell malignancy were resected in case 1. However, no abnormaities were found on gastrointestinal endoscopy after operation. Seventeen months after the resection, computed tomography(CT) showed multiple bone metastases, and the biopsy revealed signet ring cell carcinoma. Twenty months after the initial surgery, upper gastrointestinal endoscopy revealed a small mucosal lesion that showed singet ring cell carcinoma findings on biopsy. In case 2, we suspected bilateral ovarian tumors of a Krukenberg type. A complete physical examination was performed before and after ovarian surgery, but a primary site was not found. The resected bilateral ovarian tumors showed extensive lymphatic involvement with signet ring cells and prominent involvement of hilum ovarii. Therefore we considered the tumors in this case to be Krukenberg tumors. Ovarian metastasis from early stage gastric cancer is very rare, and the primary gastric cancer lesion may be very small, and easily overlooked. It may be necessary to repeat the endoscopic exploration several times if a Krukenberg tumor is suspected. Content: We report two cases of Krukenberg tumors wherein an accurate diagnosis was difficult to establish.