This is intended to be a practical review for the clinical chemist of the laboratory procedures most commonly used to quantitate hormone receptors in various cellular fractions. These procedures include use of charcoal adsorption and hydroxylapatite for intracellular receptors and of centrifugation and filtration for membrane receptors. We discuss the use of the Scatchard analysis to establish the steroid-receptor affinity and the quantity of steroid-receptor binding sites. Both pre- and post-labeled sucrose density gradient methods are outlined. One section is devoted to the direct and indirect methods used in nuclear "exchange" assays. Basic theory underlying each assay is presented, but, more importantly, we assess the advantages and disadvantages of each procedure. On the basis of this information, one may decide which assay is best suited for a particular laboratory and (or) specimen.