ABSTRACT.PLEDs constitute a distinctive but uncommon EEG phenomenon of repetitive, roughly periodic, and stereotyped lateralized complexes. Most often they have a widespread hemispheric distribution with regional predominance. Within a given record, localization of complexes is more constant than morphology which consists of polyspikes, bi- or triphasic waves, spike and wave, sharp waves, or polyphasic waves. Complexes are usually of medium voltage and are associated with suppression of normal rhythms in the same region.PLEDs are usually transient and have a close temporal relationship with acute or progressive structural lesions, most commonly stroke. Rarely PLEDs remain for years without evidence of a progressive structural lesion. There is a strong association with cerebral seizures. The latter are usually focal, sometimes showing secondary generalization; some patients have epilepsia partialis continua. Significant systemic metabolic disorders occur in about 1/4 to 1/3 of patients. PLEDs are associated with a high mortality and morbidity, with the latter including recurrent epileptic seizures.