This study investigated the expression patterns of Müllerian inhibiting substance/anti-Müllerian hormone type II receptor (MIS/AMHRII) and mRNA in various types of ovarian neoplasia and evaluated the clinical significance of MIS/AMH as a biological response modifier for MIS/AMHR-positive tumors. Reverse transcriptase polymerase chain reaction was used to detect MIS/AMHRII mRNA expression and in situ hybridization and immunohistochemistry were used to localize MIS/AMHRII mRNA and protein expression. The degree of expression was scored from 0 (no staining) to 3 (strong staining). There was no significant difference in expression intensity between MIS/AMHRII protein and mRNA on all ovarian samples whether benign or malignant. MIS/AMHRII protein and mRNA were weakly expressed on 45.45% of benign ovarian tumors. In borderline tumors, expression rates of MIS/AMHRII protein and mRNA were 77.78% with score 1.22 and 55.56% with score 1, respectively. In malignant ovarian tumors, expression rates of MIS/AMHRII protein and mRNA were 70% with score 1.23 and 75% with score 1.43, respectively. Among malignant ovarian tumors, sex cord stromal tumors showed the highest expression rate and the strongest intensity of MIS/AMHRII protein and mRNA followed by germ cell tumor and epithelial ovarian tumor. Non-epithelial malignant tumors showed stronger expression than that of epithelial tumors (P<0.05, P<0.001, respectively). In serous borderline malignant and malignant tumors, MIS/AMHRII protein and mRNA expression was 63.64 and 81.82% with expression intensity of 1.27 and 1.46, respectively, which were not statistically different from non-epithelial malignant tumors. MIS/AMHRII and MIS/AMHRII mRNA demonstrate significantly variable expression among different ovarian tumor types. Non-epithelial cell tumors show higher expression than those of epithelial cell tumors. The highest expression rate and intensity were observed on sex cord stromal tumors. MIS/AMHRII expression was not different according to the differentiation, but showed tissue-type specificity. These data support that MIS/AMH may be used as a biological modifier or therapeutic modulator in MIS/AMHRII-expressed ovarian tumors.