The biologic significance of epidermal growth factor (EGF)-related proteins and EGF receptor (EGFR) in the development and progression of human ovarian carcinoma was studied in 7 ovarian cystadenomas, 6 mucinous tumors of low malignant potential (LMP), and 25 invasive adenocarcinomas by immunohistochemistry. Results were correlated with clinicopathologic features. We also examined immunoreactivity in five serous adenocarcinomas both before and after cisplatin chemotherapy. Amphiregulin (AR) expression was observed only in mucinous tumors (4 of 8 cystadenomas, 2 of 6 tumors of LMP, and 6 of 10 cystadenocarcinomas), but was not detected in the serous tumors or clear cell adenocarcinomas. EGF, cripto, and EGFR expression was significantly higher in mucinous cystadenocarcinomas than in mucinous cystadenomas or mucinous tumors of LMP. Three of five specimens obtained at a second operation after chemotherapy had more intense or diffuse immunostaining for transforming growth factor alpha (TGF-alpha) than the initial specimens did. Coexpression of more than two of the EGF-related proteins or EGFR significantly correlated with increased surgical stage in serous and clear cell carcinoma. AR expression seems to correlate with mucinous differentiation rather than with advanced stages of ovarian tumors. Our results indicate that expression of some EGF-related proteins is greater in certain subtypes of ovarian carcinomas than in their benign counterparts and that coexpression of these proteins is associated with advanced stage in serous and clear cell carcinoma. Increased TGF-alpha expression may also be related to ovarian tumor resistance to cisplatin chemotherapy.