The year 1993 marked the centennial of the publication of Sir William Macewen's monograph, Pyogenic Infective Diseases of the Brain and Spinal Cord, and its accompanying volume, Atlas of Head Sections. As Harvey Cushing noted, the text on pyogenic diseases of the brain was a landmark in surgery of the nervous system. At the time of its publication, Macewen's work was the most comprehensive study of pyogenic brain diseases. In this paper the author reviews the state of knowledge of brain abscess existing in the 19th and 20th centuries, with particular emphasis on the late 19th century, and elucidates factors contributing to Macewen's remarkable success. His thorough knowledge of the natural history of pyogenic diseases of the temporal bone and nasal sinuses, in addition to his clear description of cranial anatomy, as illustrated in his Atlas of Head Sections, were especially important in developing his successful treatment of brain abscess. The x-ray had not yet been discovered; Macewen's diagnosis was based on clinical findings superbly illustrated by his three clinical stages of brain abscess development. His clinical observations are as relevant today as when he described them 100 years ago. Macewen recorded 25 cases of brain abscess. Nineteen of these patients came to his attention in time to undergo surgery, resulting in 18 recoveries. All five of his patients with extradural abscess recovered. These results were achieved in the era known as "the most glorious period in British surgery." Neurosurgery was in its infancy; nevertheless, even as the 20th century closes, Macewen's results still have not been surpassed.