Seven patients with decompensated posthepatitis B cirrhosis were treated with low doses of interferon alpha. The initial plasma level of HBV-DNA ranged from 3.0 to 189.3 pg/ml, and that of ALT from 37 to 156 IU/l. Liver biopsies demonstrated ongoing piecemeal necrosis. In sera of all but one patient, HBV-DNA became undetectable by hybridisation techniques within 10 to 28 weeks. Plasma HBeAg became negative in four and HBe-antibodies positive in three patients. Serum transaminase levels showed a marked initial rise 3 to 13 weeks after onset of therapy; they dropped to normal values later in all except one patient. Therapy was initiated at 1 MU (million units) three times a week for 2 weeks and was increased to 2.5 MU for 16 weeks. Later, this dosage was raised to 5 MU three times a week in some patients. Complications included variceal haemorrhage, aggravation of ascites or of encephalopathy, development of pneumonia, recurrence of spontaneous bacterial peritonitis or of gastric ulcer bleeding. One year after stopping the therapy, three patients are well and without any feature of liver decompensation. Three patients died before they could undergo a liver transplantation. In one patient treatment was interrupted because of marked exacerbation of liver cell necrosis. It thus seems possible to suppress HBeAg and HBV-DNA in patients with decompensated cirrhosis. This is important to prepare them for possible liver transplantation. Interferon should be initiated at low doses and the patients be very carefully monitored. Prophylactic therapy for bacterial peritonitis and for variceal haemorrhage is warranted.