The concept of microvascular compression (MVC) is discussed critically. The root entry or exit zone is defined: it is much shorter than generally realized. The anatomy of the intracranial vessels is considered, as well as known facts concerning trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia relating to MVC. The results of microvascular decompression (MVD) are analyzed; one-third of patients do not obtain an optimum result. The evidence used to support the hypothesis of MVC, including neurophysiology, is discussed and it is believed to be insufficient and unconvincing. The basis of MVC could be trauma of the nerve during operative dissection and "decompression." The concept of MVC might be more convincing if MVD can be shown to cure a condition such as spasmodic torticollis, which cannot be remedied by damage to or section of the same cranial nerve or nerves.