The aim of this article is to present a summarizing overview on ethnomedical aspects of koro (in Chinese called suo-yang), the panic anxiety state in which affected males believe that the penis is shrinking and/or retracting, and perhaps disappearing. While reduction of penile volume occurs physiologically due to vasoconstriction in cold temperature and intense anxiety, it is believed in certain cultures that genital shrinking leads to impotence and sterility, and eventually to death. Traditional Chinese medicine treats suo-yang, the reduction of the male principle yang, as a dangerous disturbance of the life-sustaining yin-yang equilibrium of the organism. Koro has therefore been held to be a Chinese "culture-bound" condition. However , the koro phenomenon is also known among diverse ethnic and religious groups in Asia and Africa, typically in cultures in which reproductive ability is a major determinant of a young person's worth. Koro epidemics of panic anxiety due to widespread fears of losing one's genitals, procreative ability, and even one's life, are triggered by rumors of genital disappearance supposedly caused in China by female fox spirits, in Singapore and Thailand by mass poisoning, and in Africa by sorcery, usually in the context of socioeconomic or political tension. Today, in contemporary Western societies, ideas of genital disappearance are not culturally endorsed. But historically, it should be remembered that in the late Middle Ages in Europe, a man could lose his membrum virile through magical attacks by witches. The conclusion is that the psychological disappearance of the penis is a universal syndrome that was described recently in Asia and Africa and already in Medieval Europe.