Several studies have reported a higher prevalence of chronic hepatitis C virus (HCV) infection in patients with B-cell non-Hodgkin's lymphoma and suggested a pathogenic role for HCV, but studies on hepatitis B virus (HBV) infection and non-Hodgkin's lymphoma are limited. To determine the association between HBV infection and non-Hodgkin's lymphoma, we performed a case-control study in Korea, a hepatitis B endemic area. We recruited 222 patients newly diagnosed with non-Hodgkin's lymphoma at Seoul National University Hospital between January 1997 and December 1998 as cases. Four age- and sex-matched controls were selected for each case, and the control groups comprised of 439 patients with non-hematological malignancy (control group 1) and 444 subjects with non-malignant conditions (control group 2). Relative risk of developing non-Hodgkin's lymphoma among individuals tested positive for hepatitis B surface antigen was calculated after controlling for other potential risk factors of lymphoma, such as smoking, alcohol drinking, transfusion history and HCV infection. Hepatitis B surface antigen was positive in 28 of 222 patients (12.6%) with non-Hodgkin's lymphoma compared with 32 of 439 (7.3%) in control group 1, and 21 of 444 (4.7%) in control group 2 (P = 0.001). The crude odds ratio for B-cell non-Hodgkin's lymphoma among the HBV carriers was 2.54 (1.46 - 4.45) and the adjusted odds ratio was 3.30 (1.69 - 6.45) by multivariate analysis. The present study suggests that the risk of B-cell non-Hodgkin's lymphoma is increased in HBV carriers and warrants further investigation of the possible role of hepatitis B virus in the pathogenesis of B-cell non-Hodgkin's lymphoma.