This report concerns two patients with fulminant meningoencephalitis presenting in status epilepticus with periodic lateralised epileptiform discharges (PLEDs) observed on electroencephalogram. The titer of herpes simplex virus type 1 antibody was not elevated in either serum or cerebrospinal fluid, and acyclovir was not effective for either patient. Corticosteroid therapy was dramatically effective, however, suggesting that autoimmune inflammatory diseases were the underlying systemic disorders. PLEDs can thus be associated with steroid-responsive inflammatory meningoencephalitis.