Helicobacter pylori infection has been investigated extensively in immunocompromised hosts, such as those with acquired immunodeficiency syndrome (AIDS) and organ transplant recipients. However, few reports on H. pylori prevalence in individuals with chronic HBV infection are available. The aim of this serological study is to investigate H. pylori prevalence in patients with hepatitis B. Ninety-six consecutive hospitalised patients with chronic hepatitis B were studied, together with 104 age-matched healthy individuals of similar socioeconomic status and with no evidence of hepatitis B virus infection or liver diseases. Serum samples from both groups were tested for specific IgG antibodies to H. pylori, using enzyme-linked immunosorbent assay (ELISA). Of the 96 patients with hepatitis B, 55 (57.3%) were positive for serum IgG anti-H. pylori, significantly greater than in the control group of 104, where 44 (42.3%) were positive (P < 0.05). In addition, the seroprevalence of H. pylori in the 45 patients who were positive for hepatitis B envelope antigen (HBeAg) and/or HBV-DNA was 75.6% (34), compared to 41.2% (21) in the 51 patients who were negative (P < 0.005). An increase in H. pylori prevalence is present in patients with chronic hepatitis B. Further study is needed to determine whether eradication of H. pylori will benefit these patients.