The field of steroid hormone action is well established, although it is barely more than four decades old. Pivotal experiments in the late 1950s and 1960s showed that hormone-binding components exist within nuclei of target tissues and that steroid hormones act by regulating gene expression, rather than directly influencing enzymatic processes. The understanding that steroid hormone receptors interact with the general transcription machinery and alter chromatin structure came in the 1970s and 1980s, and details of this mechanism continue to be elucidated. In addition, the discovery of rapid cellular responses to steroid hormones has led to the identification of putative membrane-bound steroid receptors that act without affecting gene transcription. As noted in the recent Institute of Medicine report Exploring the Biological Contributions to Human Health: Does Sex Matter?, the effects of steroid hormones and defects in steroid hormone receptor action have a profound impact on human health and disease. Future research directives include the development of potent, selective steroid receptor modulators, the elucidation of nongenomic steroid hormone effects, and further exploration of hormone-genome interactions.