A large outbreak of Salmonella Typhimurium infections occurred among persons who drank pasteurized, 2% milk that had been produced by a single dairy plant in Illinois. Salmonella Typhimurium was isolated from unopened containers of two lots of 2 % milk that were under the brand names of Bluebrook and Hillfarm. The milk had been sold in multiple states. The milk was sold in Jewel, Eisner, and Magna supermarkets in Illinois, Indiana, Iowa, and Michigan. Laboratory tests confirmed contamination in two batches of milk that had been processed on April 8. Located in a Chicago suburb, the Hillfarm dairy was the sole supplier of milk to 217 supermarkets operated by the Jewel Food Stores chain in Illinois, Indiana, Iowa and Michigan. The dairy was owned by the Jewel company and had been producing milk since 1968. The outbreak prompted the company to cease all dairy production on April 9, 1985. The presence of a cross connection that could have exposed pasteurized milk to raw milk was suspected as the cause of the contamination in the dairy processing plant.