We report here the first orthotopic transplant model for human ovarian cancer. Histologically-intact patient specimens of ovarian cancer were transplanted by microsurgical techniques under the capsule of the nude mouse ovary. The human tumors grew locally and gave rise to a patient-like metastatic pattern including the parietal peritoneum, colon, omentum, and ascites. The orthotopic model described here should be useful for evaluating new therapeutics and diagnostics for ovarian cancer.