Some viral infections are reported to influence the susceptibility of peripheral blood mononuclear cells (PBMC) to apoptosis, which is related to disease progression. The current study was designed to monitor apoptosis in separated PBMC subsets, CD4+ and CD8+ T lymphocytes, and CD14+ monocytes under apoptotic stimuli in patients with chronic hepatitis C. Apoptosis was induced by serum starvation and by incubation with anti-CD3 antibody and with phorbol 12-myristate 13-acetate. With the escalating severity of liver disease, susceptibility of all PBMC subsets to apoptosis increased under the apoptotic stimulus of serum starvation (P<0.05). Consequently, increased susceptibility to apoptosis was associated with diminished intracellular expression of the antiapoptotic protein Bcl-2 (P<0.05). The current observations demonstrate that the abnormality of PBMC subsets in undergoing apoptosis as a result of the down-regulation of Bcl-2 expression may contribute to viral persistence and progression of liver disease in chronic hepatitis C.