Although HBeAg positivity in immunocompromised cancer patients appears to be a risk factor for HBV reactivation (Liang et al, 1990; Yeo et al, 2000b), this has not been found to be universally the case (Lok et al, 1991; Nokamura et al, 1996), and an increased risk may be partly attributed to the presence of the pre-core/core promoter HBV mutant (i.e. HBeAg negative/anti-HBe positive), which had been associated with severe fulminant hepatitis (Omata et al, 1991; Ehata et al, 1993; Liang et al, 1994; Nokamura et al, 1996; Steinberg et al, 2000; Yeo et al, 2000a, 2000b). The gene discussed is HBE1; the disease is cancer.