Burkholderia pseudomallei, the causative agent of melioidosis, is a facultative intracellular Gram-negative bacillus which can survive and multiply in both phagocytic and nonphagocytic cells. This bacterium could also induce apoptosis in various cell types. In the present study, we extend our finding to demonstrate the role of RpoS of B. pseudomallei in apoptosis induction. Unlike the wild-type strain, the B. pseudomallei rpoS mutant strain failed to induce cytotoxicity in mouse macrophages (RAW264.7). Furthermore, the mutant produced less extensive mitochondrial membrane potential changes and caspase-3 activation in the macrophages than did the wild-type strain. These data suggest that the RpoS of B. pseudomallei plays an essential role in the regulation of cell death in mouse macrophages.