Epidemic strain Salmonella typhimurium DT104 is characterized by various multiresistance patterns. At least some of the resistance genes are organized as integrons. Resistance genes of DT104 isolates can be efficiently transduced by P22-like phage ES18 and by phage PDT17 which is released by all DT104 isolates so far analyzed. Cotransduction tests demonstrate that the resistance genes, although not organized in a unique integron, are tightly clustered on the Salmonella chromosome. The spread of resistance genes in this strain by generalized transduction is discussed.