A study on 28 patients undergoing vascular surgery was performed with the aims to confirm the postoperative decrease of serum FT3 value, to study the correlation between Euthyroid Sick Syndrome (ESS) and postoperative complications, to detect a possible correlation between markers of severity of atherosclerosis and ESS. A slight but significant decrease in postoperative FT3 value was observed (3.88 +/- 0.73 vs 3.32 +/- 1.07 p < 0.05), while we could not find any difference in pre-postoperative FT4 and TSH values. Six patients developed inflammation-related complications (Systemic Inflammatory Response Syndrome--SIRS) and they all showed a deeper postoperative decrease of FT3 value than non complicated subjects, even if the difference was not statistically significant (1st postop day 3.60 +/- 1.05 vs 2.47 +/- 0.61 p = 0.06). Finally, a strong negative linear correlation was observed between preoperative fibrinogen value and FT3 (r = -0.48). FT3 value could be a good predictor of risk for inflammatory-related postoperative complications. Preoperative FT3 value in patients with atherosclerosis is inversely correlated with markers of inflammation activity, mainly with fibrinogen.