SummaryWe have analyzed the initial clinical aspect and the clinical, electroencephalographic and biological evolution of six successive patients who developed fulminating hepatitis with coma. Three of them were able to overcome the acute period of severe hepatic failure and were completely cured after a few weeks whereas the other three progressively developed signs of irreversible brain damage and died.Once or twice a day, each of the patients was submitted to plasmapheresis. This treatment was usually associated with corticosteroids, L-Dopa, neomycin and lactulose, without any apparent influence of these drugs on the evolution of the disease. The two groups of patients were similar with respect to their initial neurological aspect but, using the possible evolution towards recovery or death as the discriminant, some biological differences seemed to be present between the two groups. We noticed that the patients with an unfavourable evolution usually had a metabolic acidosis with respiratory alkalosis ; the levels of cytolytic enzymes and arterial ammonia were higher whereas the coagulation factors were as much disturbed in one group as in the other.The evolution of the electroencephalographic disturbances was parallel to the clinical ones; the same was often true for blood urea (4 cases out of 6).The reasons why we chose plasmapheresis as the method of temporary hepatic support rather than other methods is discussed. The precautions to be taken and the possible risks are also outlined.