The dosage of estrogenic receptors (ER) was performed on 80 cytosols of human breast carcinomas "immediately operable", by using a methode consisting of a single saturating dose (5 nM) with carbon-dextran and a new immuno-enzymatic method commercialized by ABBOTT laboratories using anti-ER monoclonal antibodies. The concordance is excellent between the two methods in terms of positivity. The results are significantly higher with the ER-IEA method than with the biochemical method (p. less than 1.10(-5]. The regression of the ER-IEA method as compared to the biochemical method is linear with a regression line: Y (ER-IEA) = 0.82 X (ER-Biochem) + 0.76 (logo10 conc. fmoles/g tissue). The correlation is good between the two methods (r = 0.90). A significant relationship (p less than 0.01) has also been observed with the histological grade of the carcinoma. Finally, the immuno-enzymatic technique seems particularly well adapted to small biopsies and slightly positive tumors.