Background/Aims: In gastric cancer, the presence of estrogen receptor(ER) with variable percentages of positivity using different detection methods has been reported by several groups. The application of different detection methods may account for the difference in percentage of positivity. Although the presence of ER in gastric cancer has been demonstrated, their biologic and clinical significance in this cancer remain controversial. The aim of this study is to demonstrate ER immunohistochemically in routinely processed specimens. Methods: We studied ER in sixty cases of primary gastric carcinomas, 43 men(age ranged 34yrs-77yrs) and 17 women(24yrs-71yrs). They were operated for gastric carcinoma between 1990-1992. Immunohistochemical study for ER was carried out using an avidin-biotin technique with monoclonal ER1D5 antibody(Immuntech, France) on routinely forrnalin fixed and paraffin-embedded gastric cancer tissue of representative sections selected from gastrectomy specimen and also using same method with monoclooal antibody, NCL-ER-LH2(Novocastra, UK) on endoscopic biopsied tissue sections of 35 cases. Results: Our results showed no detectable ER in both gastrectomy and biopsy specimens, while in breast carcinoma for positive control revealed positive reaction. Conclusions: Even though the number of studied cases were not large enough but the following points support the our results; 1) in gastric cancer no ER is expressed comparing with those classic estrogen dependent tumor. 2) our result is proved not due to delayed fixation artefect or defect of monoclonal antibody. Therefore, we think that the reliability of our immunohistochemical technigue and its result are insured. (Korean J Gastroenterol 1997; 30:173-178)