We studied 13 episodes of nonconvulsive generalized status epilepticus (NGS) in 10 adults. The syndrome may start in middle or late life and is often mistaken for psychiatric disorders. Some patients have shown good retention of language abilities, except for reduced fluency, despite impairment in other higher functions. In most patients, the syndrome recurs for several years despite anticonvulsant therapy. Transitional cases of NGS with lateralizing EEG features exist, and some cases are probably due to secondary generalization from a temporal or frontal focus.