Standard dextran-coated charcoal (DCC) and sucrose gradient centrifugation assays for estrogen receptor were compared in a series of human breast cancer tissues. From a quantitative standpoint the results were remarkably similar. A simplified version of the DCC assay compared to the sucrose gradient assay yielded acceptable results. We conclude that, in spite of the lack of specificity controls inherent in the sophisticated standard assays, the simplified DCC assay might be useful if the biopsy specimen is too small to provide the number of aliquots for a standard DCC assay or sufficient protein for a sucrose gradient analysis. It also might be useful in research laboratories attempting to develop assays for multiple receptors or other constituents in a single tumor biopsy specimen.