Epidermal growth factor receptor expression in normal ovarian epithelium and ovarian cancer. II. Relationship between receptor expression and response to epidermal growth factor. Previously we have shown that epidermal growth factor acts as a mitogen for some, but not all, ovarian cancer cells in culture. In this study we examined the effect of epidermal growth factor on proliferation of normal human ovarian epithelial cells in monolayer culture. We found that epidermal growth factor stimulated twofold to fourfold increases in proliferation in epithelial cells from each of five normal ovaries (p less than 0.01). In addition, Scatchard analysis of binding of epidermal growth factor tagged with iodine 125 indicated the presence of high-affinity receptors in all of the ovarian epithelial cells and ovarian cancer cell lines. The number and affinity of receptors was similar in the normal epithelium and cancer cell lines, and there was no relationship between epidermal growth factor receptor number and responsiveness to epidermal growth factor. We conclude that human ovarian epithelial cells normally express epidermal growth factor receptors and that epidermal growth factor acts as a mitogen for these cells. Although the mitogenic response to epidermal growth factor often is attenuated in ovarian cancer cell lines, loss of responsiveness to epidermal growth factor does not appear to be due to decreased receptor expression. 