['Estrogen receptors (ERs) have been detected in gastric carcinoma cells in vivo and in vitro. Several in vitro and in vivo studies examining the potential beneficial effects of adjuvant Tamoxifen (Tmx) have shown contradictory experimental and clinical results.', 'We examined the effects of a brief Tmx pretreatment on the chemosensitivity to 5-FU of two gastric carcinoma cell lines. One of these cell lines was ER(+) and the other ER(-). Tmx was administered for 24 hours before chemotherapy.', 'We observed a significant increase in the cytotoxic action of 5-FU in both gastric carcinoma cell lines in the order of 100-155%. This increase in 5-FU cytotoxicity was not mediated by either the ER cell status or through TGF-beta 1 secretion.'] Does brief tamoxifen pretreatment enhance the chemosensitivity of gastric carcinoma cells to 5-fluorouracil in vitro?