Baylisacaris procyonis, the common raccoon ascarid, is known to cause life-threatening visceral, neural, and ocular larva migrans in mammals and birds. Two human fatalities have been previously described; however, little is known about the spectrum of human disease caused by B. procyonis. In this report, the case of a 13-month-old child who had nonfatal meningoencephalitis secondary to B. procyonis infection is presented. The suspected diagnosis was confirmed with use of newly developed enzyme immunoassay and immunoblot techniques. The diagnosis, management, and prevention of B. procyonis infection in humans is discussed. Clinical, serological, and epidemiological evaluations established B. procyonis as the etiologic agent. The child survived his infection but continued to have severe neurological sequelae. The potential for human contact and infection with B. procyonis is great. There is no effective therapy; therefore, prevention is paramount.