Status epilepticus is associated with high mortality and is a predictor of poor neurological outcome; yet the contribution of prolonged seizures to mortality and the causal sequence for neurological damage remain unclear. Many cases of status epilepticus are precipitated by illnesses that themselves are associated with increased mortality and morbidity. In studies of children, status epilepticus appears to be no better a predictor of an adverse outcome than is any seizure disorder starting at a similar age. Status epilepticus is a condition in which fast and definitive medical intervention is warranted. Random assignment to treatment groups is difficult. Evaluation of the effect of duration of seizures is also difficult, because those patients responding promptly to treatment may be quite a different population than those not responding. The study of cases of "nonconvulsive" status may provide information regarding the effect of these continuing ictal brain discharges, which can be evaluated without the confounding effects of concomitant metabolic (e.g., anoxic, pH, electrolyte) disturbances that accompany most cases of generalized status epilepticus. It is possible that appropriately designed prospective studies of status epilepticus and/or case-control studies will assist in evaluating the contribution of a prolonged seizure per se over and above that associated with preexisting or concurrent illness.