Koro is a panic state associated with the thought that one's sex organ is disappearing into the body and the outcome of which is fatal. It is most prevalent in southern China, where repeated epidemics have occurred. Koro is found only in Hans, the dominant ethnic group, but not in other minority groups in China, and is over-represented in young people under 24 years of age. That koro is limited largely to young people of Han origin along the southern coast suggests that there are cultural and social events which promote koro behaviour in young people. Based on secondary data about a largescale epidemic in southern China ten years ago, this paper examines how environmental and personal risk factors operate in a dynamic way to determine the way koro is manifested in Chinese people. Copyright © 1997 Taylor & Francis Group, LLC.