Hormone receptors play a major role in growth and hormonal therapy of breast and prostate tumors. Quantitative results from the ligand binding assays cannot determine heterogeneity in receptor expression nor can they discriminate between expression of the stromal and the tumor cells. Availability of antibodies to hormone receptors has led to the development of immunohistochemistry as a standard method for monitoring of hormone receptor expression under a microscope. However, this method is based on examination of a small number of cells. Laser flow cytometry has been extensively used for monitoring of receptor expression in human liquid tumors. As most of the hormone receptor expression is nuclear, we have developed methods for flow cytometric analysis of receptor expression in nuclei isolated from enzyme treated paraffin sections. The present report based on gated analysis of androgen receptor expression in nuclei isolated from archival formalin fixed/paraffin embedded breast tumors shows that receptor expression in aneuploid sub-populations is greater than that of the diploid cells.