Expression of CD44 standard form (CD44s) was evaluated by automated immunohistochemical analysis using the anti-CD44 A3D8 clone in 101 ovarian epithelial neoplasms including 82 primary tumors (64 carcinomas and 18 tumors of low malignant potential [LMP]), 9 lymph node metastases, 8 malignant ascites, and 2 peritoneal implants. Immunostaining was scored semiquantitatively. Tumors were graded according to the FIGO (International Federation of Gynecology and Obstetrics) classification system. Tumor stage and patient survival were determined from the patient records. While 9 of 18 LMP tumors expressed CD44s, only 15 of 64 carcinomas expressed it. In the carcinomas, univariate analysis revealed that decreased CD44s expression correlated with high tumor grade, advanced stage, and shortened survival. Loss of CD44s expression also was noted in the tumor cells in 8 of 9 lymph node metastases, 7 of 8 malignant ascites, and 1 of 2 implants. Multivariate analysis revealed that only tumor stage independently correlated with patient survival. Loss of CD44s expression determined by immunohistochemical analysis is more common in ovarian carcinomas than in LMP tumors; correlates with prognostic variables including tumor grade, stage, and survival; and may have an important role in the dissemination of ovarian cancer.