This study explored the use of thiol/disulphide homeostasis as a novel oxidative stress marker in patients with erectile dysfunction (ED). Fifty-five patients aged 40-57 were divided into two groups: Group I (International Index of Erectile Function [IIEF-5] score between 22 and 25, n = 20) and Group II (IIEF-5 score < 22, n = 35). Blood samples were used to evaluate hormone levels, lipid profile and thiol/disulphide levels. A novel, fully automated method measured plasma native thiol, total thiol and disulphide levels. Mean age, body mass index, total testosterone, HbA1c, triglyceride, atherogenic index (AIP) and total cholesterol levels did not significantly differ between Groups I and II (p > .05). IIEF-5 correlated weakly with native thiol level. Although non-statistically significant, native thiol (431 [SD: 105] mu mol/L vs. 404  mu mol/L) and total thiol (426  mu mol/L vs. 41  mu mol/L) levels were lower in the ED group compared to the controls, and disulphide (14  mu mol/L vs. 18  mu mol/L) levels were higher. Mean disulphide/native thiol and mean disulphide/total thiol ratios did not statistically differ between groups. There was a weak positive correlation between AIP and total cholesterol/HDL and disulphide and disulphide/total thiol ratios. Thiol/disulphide haemostasis levels are not a single factor in ED pathophysiology but may contribute.