Adefovir dipivoxil (ADV), a new nucleotide analogue, has demonstrated activity against lamivudine-resistant HBV both in vivo and in vitro. Herein, we present eight lamivudine-resistant patients with chronic anti-HBe positive hepatitis B treated orally with adefovir dipivoxil at 10 mg/die to evaluate the efficacy and safety of this drug and to determine the possible development of clinical ADV resistance. After 48 weeks of therapy, 4/8 (50%) patients demonstrated a complete response with normalization of alaninoaminotransferase levels (ALT, normal value < 40 IU/L) and undetectable serum HBV- DNA (< 100 copies/ml tested by a PCR assay). In 3/8 subjects (37.5%), we observed a partial response with a > 50% reduction of both ALT and HBV DNA levels. Only one patient did not respond. Adefovir was well-tolerated and no patient presented adverse events related to treatment; there were no changes in renal parameters. We conclude that in patients with anti-HBe positive chronic hepatitis B resistant to lamivudine, a 48-week ADV treatment resulted in significant biochemical and virological improvement without major adverse effects.