For quantitative assessments of sex hormone receptors in liver tissue, ligand binding assays are inconvenient, as they require large biopsies (0.5-1.0 g). The present study shows that it is possible to measure oestrogen receptors (ER) quantitatively in needle biopsy specimens as small as 10 mg by modifications of a commercial enzyme immunoassay employing monoclonal antibodies. Sucrose gradient centrifugation and the dextran charcoal method served as reference methods. A consecutive series of needle biopsies from patients suspected of liver disease were investigated. The biopsies (n = 37) had a median weight of 14 mg and cytosolic protein concentrations greater than 1 mg/ml (median 1.28 mg/ml). The median ER concentration was 20 fmol/mg cytosolic protein (range 5 to 57 fmol/mg). The intra-assay coefficient of variation was 8.9%, the inter-assay 13.2%, and the detection limit 2.7 fmol/ml cytosol. Women had significantly higher ER concentrations (median 22 fmol/mg) compared to male patients (median 16 fmol/mg) (P = 0.007). The enzyme immunoassay measures ER in liver specimens as small as 10 mg, compared to the large tissue specimens necessary for the conventional DCC assay, and the method is a convenient tool for further studies of ER in routine needle biopsies from the liver.