The normal breathing rhythm in mammals is hypothesized to be generated by neurokinin-1 receptor (NK1R)-expressing neurons in the preBötzinger complex (preBötC), a medullary region proposed to contain the kernel of the circuits generating respiration. If this hypothesis is correct, then complete destruction of preBötC NK1R neurons should severely perturb and perhaps even fatally arrest breathing. Here we show that specific and near complete bilateral (but not unilateral) destruction of preBötC NK1R neurons results in both an ataxic breathing pattern with markedly altered blood gases and pH, and pathological responses to challenges such as hyperoxia, hypoxia and anesthesia. Thus, these approximately 600 neurons seem necessary for the generation of normal breathing in rats.