The pathogenesis of liver damage in the course of hepatitis B virus (HBV) infection depends on the host's specific and non-specific immune response to various viral antigens. The role of polymorphonuclear neutrophils (PMN) in the natural immune reaction and during secondary microbial infections is well documented. Increased free radical production is associated with many pathological conditions such as shock, ischaemia or chronic inflammatory diseases. We studied the oxidative metabolism of neutrophils in patients with chronic HBV and after recovery (convalescents). The effect of the PreS1 fragment of HBV antigen on some neutrophil functions in vitro was also examined. There were significant differences in the values of spontaneous and stimulated oxidative burst of neutrophils, measured using luminol-chemiluminescence, in patients with HBV when compared with the convalescents. PreS1 antigen did not by itself induce the respiratory burst in human neutrophils but it potentiated their response to a second stimulus. Hence we observed a priming of neutrophils, for an enhanced respiratory burst, by PreS1 antigen.