Mucinous tumors of the ovary are the most common tumors arising from the common epithelium of the ovary in Korean. Distinguishing the tumor with borderline malignancy from mucinous cystadenocarcinoma is very important in determining proper therapeutic modalities and prognosis. Authors have undertaken morphometric analysis of various parameters from both borderline lesions and carcinomas of mucinous nature of the ovary. In each, five cases of the borderline and malignant tumors were subjected to be evaluated. Various cytologic and histologic parameters were analyzed using Kontron IBAS-I. 1) The most helpful parameter-for differentiation between borderline and malignant mucinous tumors is cell concentration (sensitivity 80%, specificity 80%). The discrimination value is more than 35 cells per 100 micrometer of the basement membrane length. If the cellular concentration is higher than the discriminating value, that indicates malignancy. 2) Tumor cell height, though it is other parameter of stratification, is not helpful for differentiation of the two lesions. 3) Cytologic atypia, either in size or in form, can not be a criterion distinguishing the borderline from malignancy. 4) Papillary growths can not be a criterion of either borderline and malignant lesions. 5) The degree of irregularity at tumor-stroma interface is not helpful for differentiation between borderline and malignancy.