Superoxide dismutase (SOD) is reported to be the major enzymatic defence against free radicals and common oxidants. EC-SOD is the only extracellular form of SOD present at a high concentration in vascular intima. The aims of the present study were to elucidate the role of EC-SOD in patients with coronary artery disease (CAD) and evaluate its association with free radicals, inflammation and with the severity of the disease. The study included 36 consecutive subjects with CAD being treated in the Institute of Clinical Physiology (33 males, 3 females) and 19 controls (16 males, 2 females). Each subject, after cardiac catheterisation and coronariography, was evaluated for serum EC-SOD activity, peroxy radicals, high-sensitive interleukin-6 (hs-IL-6), high-sensitive tumour necrosis factor (hs-TNFa) and high-sensitive C-reactive protein (hs-CRP) serum levels. The analysis of EC-SOD serum activity did not show any particular difference between patients and controls, while the serum levels of peroxy radicals, hs-IL-6 and hs-CRP showed a significant difference between the two groups (respectively: PPPPPr 2=0.1; Pr 2=0.14). The present study suggests a low effectiveness of EC-SOD activity in prevention against CAD and further confirms hs-IL-6 as a useful marker in diagnostic prevention and in clinical characterisation of CAD.