Background/Purpose: It has been shown that the abnormality in immune cells in chronic fatigue syndrome (CFS) patients is closely associated with the participation of TGF-beta. In order to study the relationship between TGF-beta 1 and CFS, we investigated the mRNA levels of TGF-beta 1 in peripheral blood mononuclear cells (PBMCs) in patients with CFS. Methods: Fluorescent quantitative real time reverse-transcription polymerase chain reaction (FQ-RT-PCR) was performed to test TGF-beta 1 mRNA expression in PBMCs in 63 cases of CFS, 50 cases of disease controls, and 50 cases of healthy controls. Results: The mean value of TGF-beta 1 mRNA expression in CFS patients was Delta Delta Ct = 1.17 +/- 0.58, which was significantly higher than the disease controls (Delta Delta Ct = 0.07 +/- 1.08, df = 111, p < 0.01) and the healthy controls (Delta Delta Ct = 0.00 +/- 1.63, df = 111, p < 0.01). No significant difference was detected between disease and healthy controls (p > 0.05). Conclusion: The expression of TGF-beta 1 in PBMCs is significantly elevated in patients with CFS. It might be correlated to the pathogenesis of the disease. Copyright (C) 2011, Elsevier Taiwan LLC & Formosan Medical Association. All rights reserved.