The histopathologic grade of ovarian epithelial carcinoma has generally been found to be of prognostic significance, but the grading system used has varied among published reports, and often has not been specified at all. The major proposed grading systems are reviewed, and a new system is proposed, which is modeled on the Nottingham system of breast cancer grading and is designed to be applied to all invasive epithelial carcinomas of the ovary. Results obtained in studies using this system are presented. When grading is compared with histopathologic typing of ovarian carcinoma, the latter is less valuable in predicting survival but better at predicting tumor responsiveness to chemotherapy, and can also suggest the chemotherapeutic agents to be used. Thus, both grade and type should be specified in the surgical pathology report for any ovarian carcinoma.