Tomato spotted wilt virus is an important threat to tomato production worldwide. A single dominant resistance gene locus, Sw5, originating from Lycopersicon peruvianum, has been identified and introgressed in cultivated tomato plants. Here we present the genomic organization of a 35 250 bp fragment of a BAC clone overlapping the Sw5 locus. Two highly homologous (95€resistance gene candidates were identified within 40 kb of the CT220 marker. The genes, tentatively named Sw5-a and Sw5-b, encode proteins of 1245 and 1246 amino acids, respectively, and are members of the coiled-coil, nucleotide-binding-ARC, leucine-rich repeat group of resistance gene candidates. Promoter and terminator regions of the genes are also highly homologous. Both genes significantly resemble the tomato nematode and aphid resistance gene Mi and, to a lesser extent, Pseudomonas syringae resistance gene Prf. Transformation of Nicotiana tabacum cv. SR1 plants revealed that the Sw5-b gene, but not the Sw5-a gene, is necessary and sufficient for conferring resistance against tomato spotted wilt virus.