understanding the nature of rapid (nongenomic) steroid signaling depends upon identifying the protein(s) which binds hormone at the cell periphery and mediates the initial signal transmission. this book juxtaposes identifications from different laboratories and collectively presents several possibilities: nuclear steroid receptors in nonnuclear locations, other known membrane receptors with additional steroid binding sites, enzymes, transporters, receptors for blood-borne steroid-binding proteins, and unique, previously undescribed proteins.