24 patients with fulminant hepatic failure who had deteriorated to grade-IV coma were treated by repeated periods of haemodialysis with a polyacrylonitrile membrane. 9 patients fully recovered consciousness, and 8 (33%) survived to leave hospitals. These results are to be compared with those of conservative management alone (15% survival in 53 cases) and those obtained initially with charcoal haemo-perfusion (38%). Of the 16 treatment failures, cerebral oedema was found at necropsy in 13 (18%). Whether this would have been less of problem if treatment had been started earlier in the course of the illness remains to be determined.