Throughout his illustrious career, Percival Bailey made numerous contributions to the fields of neurology, neuroanatomy, psychiatry, neuropathology, and, of course, neurosurgery. His expertise, his curiosity about the nervous system, and his desire to examine it from all angles were unique. With the exception of Harvey Cushing, Dr. Bailey made some of the greatest contributions in the area of neuro-oncology at the turn of the last century. In this essay the authors summarize the key episodes of Bailey's life and discuss his impact on the classification and treatment of human brain tumors.