An outbreak of epidemic hysteria, in which 210 students at a North Carolina elementary school became ill and 102 were evaluated in hospital emergency departments, is described in terms of an outbreak of infectious disease. The outbreak began when a radiator boiler was fired for the first time in the 1985-1986 school year. The most common symptoms were headache, light-headedness, abdominal pain, and nausea; anxiety was later proposed to be the agent of illness. The outbreak appeared to have propagated by friend-to-friend transmission of anxiety within social (grade, race, and sex) cohorts, and by other audiovisual cues in the absence of person-to-person contact. An environmental survey found no plausible toxic or infectious cause of the outbreak. Separation of vectors and susceptible hosts preceded recovery from the outbreak, and reassurance and discussion of the findings of the investigating team with students, teachers, and parents may have prevented the recurrence of symptoms by alleviating anxiety.