Inflammasomes are macromolecular complexes that mediate inflammatory and cell death responses to pathogens and cellular stress signals. Inflammasome formation leads to activation of both caspase-1 and caspase-8. We have studied the molecular interactions important for assembly of the AIM2 inflammasome and for procaspase-8 recruitment and activation. AIM2 is a member of the PYHIN (pyrin domain (PYD) and HIN domain-containing) family and is activated in response to cytosolic DNA. Upon activation, AIM2 oligomerises and recruits the adaptor protein ASC. ASC is composed of an N-terminal PYD, with which it mediates a homotypic interaction with AIM2 PYD and a C-terminal CARD domain, with which it recruits procaspase-1. We show that procaspase-8 interacts with both ASC and AIM2 via interactions between the tandem DEDs of procaspase-8 and the PYDs of ASC and AIM2. Mutations on ASC PYD that disrupt its self-association also disrupt interaction with AIM2 and procaspase-8 suggesting that that either ASC PYD self-association is important for the different interactions or that the interaction mode between the three domains is similar. However, swapping of the PYDs between ASC and AIM2 disrupted inflammasome function arguing against identical surfaces being used for all three interactions. Furthermore, we show that procaspase-8 is efficiently recruited to specks formed by ASC alone but is only activated in specks containing both ASC and AIM2. This indicates a more stringent requirement for procaspase-8 activation than for its recruitment. The inflammasome does not just cluster caspases, but also promotes a specific orientation of procaspase-8 that permits activation.