TNF superfamily members (TNFRSF) and Toll Like Receptors (TLRs) recruit the adaptor kinase RIPK1 to promote pro-survival and pro-inflammatory signalling. In addition to its pro-survival activity, RIPK1 also a role in caspase-8 dependent apoptosis and has been implicated in RIPK3-MLKL-mediated necroptosis. The enigmatic role that RIPK1 plays led us to examine the phenotype of Ripk1-/- mice. We found that on a C57BL/6 background, Ripk1-/- mice die within minutes of birth with systemic cell death and inflammation. Unlike a previous report, on the C57BL/6 background, Tnfr1 deficiency did not rescue Ripk1-/- lethality. However, deletion of Myd88, a key adaptor at some TLRs and IL-1R, did rescue Ripk1-/- lethality at birth, with the mice having reduced cell death and a reduction in markers of inflammation. Surprisingly, deletion of either of the essential necroptotic proteins, Ripk3 or Mlkl, both also led to a rescue of the Ripk1-/- lethality. These double knock-out mice phenocopied the Ripk1-/-Myd88-/- knock-outs. Despite surviving birth, all three of the compound knockouts succumbed by day five, and at P3 had both hypoglycaemia and extensive intestinal apoptosis. To test the role of apoptosis in lethal neonatal phenotype of the mice, we generated Ripk1-/-Ripk3-/-Casp8-/- mice. These mice were both viable and fertile. Our data shows that necroptosis is able to either initiate or drive a lethal inflammatory cascade.