We report that a modified dextran-coated charcoal (DCC) assay, including the addition of sodium molybdate and 5% DCC stripping of endogenous hormone, detected higher estrogen receptors (ERs) than those by the conventional assay. ERs in 21 gastric adenocarcinoma were determined by the modified DCC assay; 13 patients had ERs of 2.5 to 520.2 fmol/mg protein with a mean dissociation constant of 1.9 X loP"' M. The remaining 8 patients had no detectable amount of the receptor. There were no differences between the ER-positive and ER-negative groups in clinico-pathologic characteristics such as age, sex, tumor size, location, gross appearance, invasive depth, invasion of lymph vessel or vein of stomach wall, nodal involvement, peritoneal dissemination, liver metastasis, and curability. Histological analysis, using Japanese, Lauren's, or Ming's classifications, all revealed no differences between the ER-positive and -negative groups. The survival rate was identical for the 2 study groups. These results suggest that the presence or absence of ERs in gastric adenocarcinoma does not correlate to either biologic or clinicopathologic characteristics of this tumor; the role of ERs in human gastric cancer remains to be elucidated.