On April 20, 2012, the CDC announced an investigation into an outbreak of Salmonella I 4, [5], 12:i:- infections linked to exposure to feeder rodents. Cases had been detected in at least 22 states. The rodents were sold as food for pet reptiles and amphibians. This outbreak strain had previously been implicated in a 2009 outbreak in the United Kingdom and a 2010 outbreak in the United States; both outbreaks were linked to frozen feeder rodents from Biggers & Callham, LLC D.B.A. MiceDirect. Between August 29, 2011 and February 2, 2012, a total of 46 cases were reported. The median patient age was 11 years (range: <1–69 years); 37% were aged ≤5 years, and 52% were male. Of the 12 patients interviewed, 4 reported hospitalization, 20 (74%) reported reptile or amphibian exposures, and 15 (56%) reported feeder rodent exposure. For 12 patients who recalled the types of rodent contacted, five (42%) reported exposure to live rodents, four (33%) to frozen rodents, and three (25%) to both live and frozen rodents. Seven (58%) patients reported exposure to mice, two (17%) to rats, two (17%) to both mice and rats, and one (8%) was unsure. No patients reported exposure to rodents purchased from the same pet store. Frozen mice specimens from two North Carolina pet stores where two patients purchased feeder rodents yielded the outbreak strain. Tracing the source of these mice has been difficult for investigators because of complex breeder and supplier networks and inadequate records. However, two breeders supplying pet stores from which patients had purchased rodents had received mice from the company implicated in the 2009 and 2010 outbreaks. Given the wide distribution of illnesses, rodent suppliers, and pet stores, the outbreak strain might now be endemic in feeder rodents.