Previous studies in breast and bladder cancer have suggested that epidermal growth factor receptor is expressed by only a proportion of cancers and is associated with poor clinical outcome. We used a monoclonal antibody specifically reactive with the extracellular domain of the epidermal growth factor receptor to localize this receptor immunohistochemically in frozen sections of normal ovary and epithelial ovarian cancer. Normal ovarian epithelium was found to express epidermal growth factor receptor in all cases. Among 87 ovarian cancers, however, 23% did not express immunohistochemically detectable receptor. Epidermal growth factor receptor expression was not related to histologic grade or stage, but was associated with poor survival (p less than 0.05). The median length of survival of patients with tumors that did not express epidermal growth factor receptor was 40 months compared with 26 months in patients with tumors that did express epidermal growth factor receptor. As in breast and bladder cancer, expression of epidermal growth factor receptor in ovarian cancer appears to be a poor prognostic factor.