Six persons developed genetically matched, laboratory confirmed, E. coli O157:H7 infections in Minnesota. The illnesses were subsequently linked to the consumption of steaks produced by Stampede Meat, Inc., of Chicago, Illinois. The steaks had been blade tenderized and injected with marinade. The steaks were sold throughout the USA and Canada, to restaurants, retail stores, and institutions. The Minnesota cases had purchased vacuum-packed, frozen steaks from door-to-door vendors. Additional cases were subsequently identified in Michigan and Kansas and nine other states (unknown).