This fully updated edition targets not only those assays directly involved in the discovery of GPCR-active compounds but also those involved in cell-based experiments designed to study physiological responses. Whether coming from academia or industry, or being an experienced researcher or a newcomer to the field, the reader will find accessible methods and protocols that cover the latest developments on receptor purification, molecular biology, recombinant engineering, and analytical techniques that enable the real time monitoring of the complex GPCR signaling cascade and identification of potential drug targets. Written for the highly successful Methods in Molecular Biology series, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls.