Encephalitic syndromes are a common medical emergency. The importance of early diagnosis and appropriate treatment is paramount. If initial investigations for infectious agents prove negative, other diagnoses must be considered promptly. Autoimmune encephalitides are being increasingly recognized as important (and potentially reversible) non-infectious causes of an encephalitic syndrome. We describe four patients with autoimmune encephalitis--3 auto-antibody positive, 1 auto-antibody negative--treated during the last 18 months. A comprehensive review of the literature in this expanding area will be of interest to the infectious diseases, general medical and neurology community.