Between December, 2005, and January, 2006, the Minnesota Department of Health (MDH) identified four human cases of Salmonella Typhimurium that matched each other by PFGE, pulsed field gel electrophoresis. All of the initial Minnesota cases attended the same junior high school where two of the cases handled snakes in the science classroom. One of the other cases visited the science classroom. Environmental samples from the school's science classroom and from samples of frozen vacuum-packed mice were tested. Tests showed the presence of a matching strain of Salmonella Typhimurium. Through PulseNet, additional cases were identified. Recent exposure to snakes fed vacuum-packed rodents continued to be a risk factor for illness. The outbreak strain of S. typhimurium was isolated from a Pennsylvania case's frozen rodents and from a Michigan case's pet snake. The mouse breeding facility in Texas was investigated. The outbreak strain was also isolated from the supplier's rodent facility.