In the decade since its initial description in the Journal, ¹ Escherichia coli O157:H7 has emerged as a major cause of both sporadic cases and outbreaks of diarrhea in North America. The first report described outbreaks of gastrointestinal illness that were associated with the consumption of undercooked ground beef from a chain of fast-food restaurants. At the time, little was known about the pathophysiology, epidemiology, or clinical sequelae of infection with E. coli O157:H7. Since that report, several studies have shown that infection with E. coli O157:H7 is responsible for most cases of the hemolytic–uremic syndrome, which is a major cause . . .