A 69-year-old male was hospitalized in January 1999 because of visceral leishmaniasis. He had also suffered from anti-hepatitis C virus (HCV)-positive chronic hepatitis for years. All serum hepatitis B virus (HBV) antigens and antibodies were negative except for anti-HBc. The patient was treated with amphotericin B cholesteryl sulfate (2 mg/kg twice a day for 7 days, iv). Fever disappeared on the 3rd day of treatment, the clinical condition improved rapidly and the patient recovered. In May 1999 the patient developed icteric HBsAg-negative acute hepatitis (aspartate aminotransferase 722 U/l; alanine aminotransferase 988 U/l). Anti-HBc IgM was positive and HBV-DNA was detected in serum by PCR. Anti-HAV IgM was negative. A serum sample obtained on presentation and stored at -80 degrees C was retrospectively tested and found positive for HBV-DNA. In July 1999, complete remission of acute hepatitis and seroconversion to anti-HBs was observed. We suppose that a moderate depression of the immune system, probably associated with leishmaniasis, may have enhanced HBV replication in the patient who had an HBsAg-negative 'silent' HBV infection. Restoration of the immune system after successful antiprotozoan therapy might have induced cell-mediated necrosis of the HBV-infected hepatocytes and seroconversion to anti-HBs.