New Mexico health officials initially identified eight cases of Salmonella Typhimurium that shared a common genetic fingerprint (PFGE, pulsed-field gel electrophoresis) pattern. A review of PFGE patterns of other Salmonella Typhimurium cases in the USA revealed at least 31 cases from nine states. The illnesses were linked with the purchase of ground beef from outlets of a national grocery store chain. A traceback investigation found that the beef had originated from a common supplier to the grocery store. The common supplier used three different plants to process the meat. Inspectors determined that the company's practices conformed with production guidelines. No product recalls were made. A sample of leftover, frozen, ground beef, was tested. Salmonella Typhimurium with the same PFGE pattern was identified.