An outbreak of E. coli O157:H7 infections was first identified in the region around Saint Louis, Missouri. Cases were found in Saint Louis, Jefferson, Saint Charles, and Saint Clair counties and in the city of Saint Louis. The cases ranged in age from 1 to 94. At least six persons were hospitalized. Many of the cases had eaten items from salad bars prior to becoming ill. On October 28, Illinois state health officials revealed that they were investigating an illness that might be linked to the outbreak in Missouri. The link was not described. On October 31, health department officials acknowledged that Schnucks salad bars were a focus of the investigation, however other sources had not been excluded. Cases were identified in Minnesota and Missouri that were linked to college campuses. Additional cases were found in other states; the exposure location in these states was not described. Traceback analysis determined that a common lot of romaine lettuce, from a single farm, was used to supply the Schnucks' grocery stores and the college campuses. The lettuce was sold to Vaughn Foods, a distributor, that supplied lettuce to the university campus in Missouri, but records were not sufficient to confirm that this lot was sent to this university campus. Preliminary findings of investigation at farm did not identify the source of the contamination.