Systemic inflammatory response syndrome (SIRS) is a medical condition in which the all-organ microcirculation is affected including nervous system. We describe neurological findings in 64 patients with SIRS at Hospital das Clínicas of Sao Paulo University School of Medicine; 45.3% were male and 54.7% female; their age ranged from 16 to 95 years old. SIRS was caused by infection in 68.8% of patients, trauma in 10.9%, burns in 7.8%, and elective surgery in 4.7%. The central nervous system involvement occurred in 56.3% of patients and was characterized as encephalopathy in 75%, seizures in 13.9%, non-epileptic myoclonus in 2.8%, and ischemic stroke in 8.3%. The magnetic resonance imaging, cerebrospinal fluid and electroencephalographic changes were unremarkable in encephalopathic patients. Neuromuscular disorders were diagnosed in 43.7%. Critical ill polyneuropathy was characterized in 57.1%, critical ill myopathy in 32.1%, demyelinating neuropathy in 7.2%, and pure motor neuropathy in 3.6%. Nerve and muscle pathological studies dismissed inflammatory abnormalities. The identification of these conditions has important economic implications and may change the critically ill patients' prognosis.