Autoantibodies against the N-methyl-D-aspartate receptor (NMDAR) have been associated with a complex encephalitis syndrome, which was first described in a case series of 12 young women presenting with a consistent clinical course including movement disorder, psychiatric disturbance and encephalopathy, in whom ovarian teratomas were subsequently found. Since then, it has been shown that many cases are not associated with tumours, and the condition may also affect male patients and children. NMDAR antibodies may be associated with diverse clinical pictures, including isolated psychosis. The spectrum of disease associated with NMDAR antibodies and the optimal immunomodulatory management of these patients is not yet well understood. We present three cases: a patient with musical hallucinations and seizures who responded to treatment with rituximab and intravenous immunoglobulin, a case of Rasmussen's encephalitis who showed no response to treatment with steroids and plasma exchange, and a complex seronegative case with ovarian teratoma, auditory perceptual changes, dystonia and a rapidly progressive CNS syndrome who died despite treatment. The clinical features and responses to therapy are described and discussed.