With more than half of drug targets based on GPCRs, translating into billions in worldwide sales, there is great interest in finding high-resolution structures for recombinantly expressed GPCRs, discovering novel drug interactions, and designing tailor-made, structure-based drug therapies that display improved efficacy and selectivity with lesser side effects. This book describes the physiological role of GPCRs and their involvement in various human diseases. Chapters present current approaches in drug discovery that include target selection, establishment of screening, functional assays for GPCRs, and the continuous de-orphanization process of orphan GPCRs. The book also covers recombinant GPCR expression for drug screening and structural biology, different methods to obtain structural information on GPCRs, and the importance of bioinformatics.