An F2 population of 224 individuals derived from a bacterial blight resistant cotton line S295 (Gossypium hirsutum L.) carrying the B12 resistance gene, and a susceptible line, Pima S7 (G. barbadense L.), was inoculated with Xanthomonas axonopodis pv. malvacearum (Xam) Race 18, causal agent of bacterial blight, to survey their resistance or susceptibility. The phenotype segregation in the F2 population indicated that the bacterial blight resistance gene, B12, is a single dominant gene. Simple sequence repeats (SSR) markers were used to survey the linkage to the B12 resistance gene. Two SSR markers, CIR246 and JESPR156 on Chromosome 14, were found closely linked to B12 with a genetic distance of 0.9cM and 6.17cM, respectively. Comparisons of genetic and physical maps were used to delineate the location of the B12 locus to a region of 941 kb.