The pterygopalatine ganglion (PPG), often described as the Piccadilly Circus of the Face, is of great importance to anesthesiologists, pain physicians, neurologists and surgeons, and its blockade is becoming more and more popular as our understanding of the cholinergic mechanisms of headache improve. It is also known as the sphenopalatine ganglion, Meckel’s ganglion or the Nasal ganglion. Recent research has shed important light on the neuroanatomy and neurophysiology of this ganglion and its relationship with the trigeminal ganglion, and, more important, its role in the pathophysiology of vascular or primary headaches. The authors discuss in detail these aspects as well as the applied macroanatomy, sonoanatomy, surface anatomy and microanatomy of this ganglion in this book, including popular techniques of performing the pterygopalatine ganglion block.