A randomised controlled trial was conducted in 29 HBV carriers who had been HBs and HBe antigen positive for more than six months. Fifteen patients were treated with ARA‐AMP 10 mg/kg/ day given as intramuscular injections 12 hours apart for five days followed by 5 mg/kg/day for 23 days. The 14 controls received no treatment. Serum HBV‐DNA polymerase, and HBV‐DNA decreased in all patients during therapy. Six treated patients lost serum HBV‐DNA polymerase, HBV‐DNA and HBeAg, HBsAg concentrations decreased, and five developed anti‐HBe. One of these six patients lost HBsAg and developed anti‐HBs. No such changes were observed in the control group over a similar 18 month period of observation. A four week course of ARA‐AMP inhibits HBV replication and in a significant minority of patients this is long lasting and is associated with a reduced level of inflammatory activity in the liver.