These essays offer a state-of-the-art appraisal of the current status of steroid hormone receptors and capture the controversy concerning the actual intracellular localization of steroid hormone receptors. The contributors review the evidence on the origins of the steroid hormone receptor concept, on the relationship between nuclear hormone receptor retention and a steroid induced response, on the nuclear components responsible for retention within the nucleus, and on the heterogeneity of steroid hormone receptors both in terms of their nature and distribution. They also provide a critical review of histochemical methods for locating steroid hormone receptors, in addition to chapters on autoradiographic and immunohistochemical techniques pertaining to the intracellular location of steroid hormone receptors. Among the contributors is Professor E.V.Jensen, who developed the classical "to step" model.