During the 15th and 16th centuries in England, there were five epidemics of a disease characterized by fever and profuse sweating and associated with high mortality. This disease became known as the English sweating sickness. The first epidemic occurred during 1485 at around the time of Henry Tudor's victory at Bosworth Field, and the last took place during the reign of Edward VI in 1551. The disease tended to occur during the summer and early autumn. The relatively affluent male adult population, particularly the clergy, seemed to suffer the highest attack rates, and, except in one epidemic, the disease appears to have attacked only individuals native to England. Despite the reputation of the English sweating sickness as a disease with a high fatality rate, records of burials and wills in Chester suggest that the 1551 epidemic did not have a marked effect on the demographics of the population. The etiologic agent is still unknown, although an enterovirus seems to this author to be the most likely pathogen.