Caspase-11–Dependent Pyroptosis Inflammasomes are multiprotein complexes that assemble to initiate immunity to a variety of microorganisms, as well as to sterile tissue injury. Although a role for caspase-1 downstream of inflammasomes is well characterized, the discovery that caspase-1 knockout mice were also deficient in caspase-11 has led to a reassessment of the function of caspase-11. Aachoui et al. (p. 975 , published online 24 January; see the Perspective by Cemma and Brumell ) now demonstrate that caspase-11 is required for immunity against cytosolic bacteria in mice. Only bacteria that were able to access cytosol-activated caspase-11–dependent pyroptosis, an inflammatory type of cell death. This function of caspase-11 appeared to be independent of canonical inflammasomes.