ABSTRACT. Isolates of extended-spectrum cephalosporin (ESC)-resistant Salmonella enterica serovar Typhimurium obtained from two different farms in Fukushima Prefecture, Japan, in 2007 were characterized in order to determine the genetic basis of resistance. ESC resistance in the two isolates was mediated by an AmpC β-lactamase encoded by the bla CMY-2 gene, which is located in a large selftransmissible plasmid in each isolate. The sizes of the bla CMY-2 -carrying plasmids were different. The replicon types of the plasmids were I1-I and A/C. The results of macrorestriction analysis and phage typing suggest a close relationship between both isolates. This is the first report of ESC-resistant S. Typhimurium isolated from cattle in Japan.