The levels of lipopolysaccharide (LPS)-induced interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) expression in culture of peripheral blood mononuclear cells (PBMC) and the plasma levels of IL-6 and TNF-alpha in the patients with obstructive sleep apnea syndrome (OSAS) were measured and the relationship between OSAS and IL-6 or TNF-alpha expression studied. Both IL-6 and TNF-alpha were detected by using ELISA in 22 patients with OSAS and 16 normal controls. The levels of LPS-induced IL-6 (787.82 +/- 151.97 pg/ml) and TNF-alpha (4165.45 +/- 1501.43 pg/ml) expression in the supernatant of the culture of PBMC and plasma level of IL-6 (50.67 +/- 4.70 pg/ml) and TNF-alpha (299.09 +/- 43.57 pg/ml) in the patients with OSAS were significantly higher than those in the normal controls (in the supernatant of the culture of PBMC: 562.69 +/- 197.54 pg/ml and 1596.25 +/- 403.08 pg/ml respectively; in the plasma; 12.69 +/- 2.75 pg/ml and 101.88 +/- 21.27 pg/ml respectively). There were significantly positive correlation between the levels of IL-6 and TNF-alpha and the percentage of time of apnea and hyponea, as well as the percentage of time spending at SaO2 below 90% in the total sleep time. It was concluded that LPS-induced IL-6 and TNF-alpha levels as well as plasma IL-6 and TNF-alpha levels in the patients with OSAS were up-regulated, which may be associated with the pathogenesis of OSAS.