This book overviews purinergic receptors that are playing key roles in human and pathophysiological processes. The book elaborates on how selective P1 and P2 modulators have been developed as therapeutics for a variety of diseases. It also provides an overview of current perspectives in the design of purinergic receptor modulators and future challenges such as the availability of selective ligands for all receptor subtypes. Divided into 12 chapters, this comprehensive volume also offers a multidisciplinary perspective on the historical evolution, starting with a chapter devoted to the roots and early discoveries of adenosine and its receptors, followed by a twenty-year retrospective on the synthesis, properties, and functional potential of adenosine receptor ligands, probes, and functional conjugates. In the next chapters, experts in the field delve into topics such as the therapeutic potential of adenosine receptor ligands in wound healing and fibrosis, the therapeutic benefits of A2A receptor antagonists, the A2B adenosine receptor as a target for brain ischemia or demyelination, the development and latest advancements in clinical trials of A3 adenosine receptor ligands. Other chapters describe bifunctional tools to study adenosine receptors, allosteric modulators of adenosine receptors, and new computational approaches to inspect adenosine receptor-ligand recognition processes. Furthermore, the book discusses the role of P2X4 receptors in immunity and inflammation. The final chapters illustrate CD73 inhibitors as antitumor agents, and bacterial ectonucleotidases as underexplored antibacterial drug targets. This book is a valuable resource for scholars working in the field of medicinal chemistry, as well as researchers in the industry, providing readers with a comprehensive understanding of adenosine receptor biology and its therapeutic potential.