Hepatitis B virus (HBV)-infected individuals are occasionally used as donors for bone marrow transplantation (BMT). We studied the rate of HBV infection and the clinical expression of the associated liver disease in patients receiving marrow from HBsAg+ donors. We performed a retrospective survey in 14 BMT units in Italy in which all BMTs performed between 1984 and 1994 were reviewed and those involving HBsAg+ donors were identified. Donors and recipients were analyzed for HBV markers and liver disease. A total of 24 of 2,586 patients (0.9%) had received an HBsAg+ marrow. HBsAg became detectable in 22% of pre-BMT HBsAg- patients, but only 5.5% became chronic HBsAg carriers. Antigenemia developed more frequently in anti-HBs- compared with anti-HBs+ patients independently of passive prophylaxis with hyperimmune anti-HBs Ig, although the difference was not significant. Severe liver failure with death occurred in 21% of patients, which was a value greater than that generally observed after BMT in our units (3.7%). Patients with an anti-HBe+ donor had higher frequency of liver failure (28% v 0%) and alanine aminotransferase peaks as compared with those of patients with an HBeAg+ donor. Liver failure was not observed in anti-HBs+ recipients. The use of HBsAg+ donors, particularly if anti-HBe+, increases the risk of severe liver disease in BMT recipients. Anti-HBs positivity may prevent severe liver damage.