Critical illness neuropathy is an axonal polyneuropathy recognized more frequently in adult intensive care patients with sepsis and multiple organ dysfunction. In children the diagnosis is rarely made. Within 1 year the authors observed two children with critical illness neuropathy. Both patients, a male 6 years, 6 months of age with a brain contusion and a male 2 years, 6 months of age who underwent craniectomy for Crouzon's disease, required prolonged mechanical ventilation and developed sepsis with multiple organ dysfunction. Three to 4 weeks after successful treatment of the sepsis, a flaccid tetraparesis was noticed in both patients. Laboratory investigations of blood and cerebrospinal fluid and spinal magnetic resonance imaging revealed normal results. Electrophysiologic examinations were indicative of an axonal polyneuropathy. Spontaneous improvement occurred within several months. It is likely that critical illness neuropathy occurs more often in critically ill children than previously thought. Careful neurologic examination and early electrophysiologic investigations are necessary to establish the diagnosis. Important differential diagnoses of acquired lower motor neuron weakness in pediatric intensive care medicine are discussed.