The actor-patient has evolved over the past several years from a purely passive live mannequin, upon whom the techniques of physical examination may be demonstrated before a large audience, to an active participant in the educational process. Professional actors have been trained to simulate the history and the abnormal physical findings of a neurological disease and to submit to interrogation and examination by medical students, interns, residents, and other trainees. They may also evaluate the students' performance. Dr. Barrows, a pioneer in this development, provides in a brief monograph an apology for this innovative pedagogical device, a review of its use in other medical fields, an anecdotal account of his own experiences, and many helpful suggestions for those who may wish to follow in his footsteps. A sample protocol for the simulation of acute multiple sclerosis in a young woman conveys an idea of the possibilities of the method. The