Eighteen heterosexual HBsAg carriers with anti-HBe- and HBV-DNA-positive chronic hepatitis B (CHB) were randomly assigned to receive human lymphoblastoid interferon (ly-IFN) at a dose of 5 MU/m2 i.m. three times a week for 6 months (ten cases) or no treatment (eight cases). All patients were followed for 24 months after IFN discontinuation and received a second liver biopsy. During the 6 months of treatment all patients had a progressive reduction of serum HBV-DNA levels, and at the end of therapy nine out of ten were HBV-DNA-negative and had normal ALT values. None of the untreated patients became persistently HBV-DNA-negative or showed significant variations of ALT levels. During the post-treatment follow-up, from 1 to 17 months after ly-IFN discontinuation, eight of the nine responders (89%) had recurrent or persistent reappearance of HBV-DNA in the serum and reactivation of the liver disease activity, with an ALT peak in four of them. On the post-trial liver biopsy seven of the eight relapsed patients showed persistence of HBcAg reactivity with no significant difference in the percentage of positive cells with respect to the pre-treatment liver specimen. Histological features improved in four treated patients, worsened in one untreated case and were unchanged in the remaining patients. These results indicate that ly-IFN shows a transient antiviral effect in the therapy of anti-HBe- and HBV-DNA-positive CHB. The 6-month treatment regimen employed in this study seems insufficient for eradicating the replicating virus from the liver cells in the majority of patients and consequently does not appear to prevent HBV reactivation after IFN discontinuation.