Purpose: To evaluate thiol-disulphide homeostasis - a novel, easily calculated, readily available, and relatively cheap oxidative stress marker - in radiation workers and compare the results with healthy controls.Materials and methods: A total of 108 participants were enrolled in the study including 63 hospital workers occupationally exposed to ionizing radiation in the units of interventional radiology, interventional cardiology and nuclear medicine. A control group consisted of 45 individuals staff in the same hospital. Serum thiol-disulphide homeostasis measurement was investigated via the spectrophotometric method newly described by Erel and Neeliolu.Results: The mean serum native thiol levels of radiation workers (528.9686.42mol/l) was significantly lower than control subjects (561.05 +/- 104.83mol/l) (p=.045). The mean serum total thiol levels of radiation workers (547.70 +/- 91.50mol/l) was lower than control subjects (580.36 +/- 112.24mol/l). Nevertheless, there was no significant difference between total thiol of exposed workers and controls.Conclusions: The results show that long-term low dose ionizing radiation may lead to oxidative stress and have side-effects in antioxidant thiol groups. We may suggest supporting radiation workers by safe antioxidant nutritional formulations and following up via both physical dosimetry and biodosimetric methods.