Technical Abstract: Bordetella bronchiseptica causes respiratory disease in swine, yet there are no studies examining the interaction of B. bronchiseptica with swine alveolar macrophages. A swine isolate of B. bronchiseptica (MBORD846) was able to adhere to, and survive intracellularly in swine alveolar macrophages, but the relative ability of the bacteria to accomplish these functions was dependent on its phenotypic phase and culture conditions. More bacteria were seen extracellularly as well as intracellularly when MBORD846 was cultures at 23 C; however, more bacteria cultures at 37 C survived intracellularly. Similar results were seen in experiments performed with an isogenic Bvg phase-locked mutant of B. bronchiseptica (MBA4) cultures at 37 C or 23 C, indication that another temperature dependent locus in addition to bvg may play a role in adhesion and intracellular survival. B. bronchiseptica was cytotoxic for swine alveolar macrophages in a bvg dependent manner, but no evidence for the induction of apoptosis was found. The cytotoxicity of B. bronchiseptica for alveolar macrophages, and its ability to survive phagocytosis, are no doubt important to escape from immune clearance mechanisms and establish infection, and could leave the host susceptible to secondary respiratory pathogens.