During the period of February 1972 until February 1976, we documented six cases of influenza A-associated acute encephalopathy. The illnesses occurred during periods of influenza A activity in our community. The encephalopathy was invariably preceded by an upper respiratory tract infection, and, thereafter, patients soon became confused, vomited, and showed noticeable restlessness. Patients then followed either of two courses, some becoming comatose within 24 hours and others improving rapidly within three days or less. None of these patients exhibited the hepatic and biochemical abnormalities associated with Reye's syndrome. All patients survived but some had sequelae. The syndrome of influenza-associated acute encephalopathy deserves wider recognition.