Objective: The aim of this study was to determine tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) release in response to platelet-activating factor (PAF) induction in peripheral blood mononuclear cells (PBMCs) from chronic hepatitis B virus (HBV) carriers. Methods: Subjects were grouped into three subgroups. The mean age was 37+/-10 years. Group A (n=15), group B (n=10) and group C (n=9) subjects were HBV serology-negative, had natural immunity after recovery from an acute HBV infection, and were chronic HBV carriers, respectively. Results: Compared with group A, PBMCs from naturally immune subjects and chronic HBV carriers produced significantly higher amounts of TNF-alpha and IL-6 in response to PAF. In chronic HBV carriers, TNF-alpha (1,633.3+/-793.7) and IL-6 (2,533.3+/-466.3) production was statistically lower than TNF-alpha (2,630.0+/-727.3) and IL-6 (3,870.0+/-728.4) obtained from naturally immune subjects to HBV. Conclusion: Differences of TNF-alpha levels between chronic HBV carriers and naturally immune subjects suggest that TNF-alpha may be a critical mediator of HBV clearance. Copyright (C) 2004 S. Karger AG, Basel.