Obstructive sleep apnea syndrome (OSAS) is commonly associated with endothelial dysfunction, atherosclerosis and cardiovascular disorders. On the basis of this observation, our aim was to examine the oxidative status and the matrix metalloproteases (MMP) profile in a group of subjects with OSAS. We enrolled 48 subjects with OSAS defined after a 1-night cardiorespiratory sleep study, who were subsequently subdivided in two subgroups according to the severity of OSAS (low grade = L-OSAS; high grade= H-OSAS). We measured the parameters of oxidative stress, such as lipid peroxidation, protein oxidation, total antioxidant status (TAS), nitric oxide metabolites (NOx), and the plasma concentrations of the gelatinases (MMP-2 and MMP-9) and their tissue inhibitors (TIMP-1 and TIMP-2). We found a significant impairment of oxidative status in H-OSAS compared to L-OSAS and higher plasma levels of MMP-9 and TIMP-1 in H-OSAS compared to L-OSAS. In this study we observed a positive correlation between TBARS and MMP-9, a positive correlation between PC and MMP-9, and a negative correlation between NOx and MMP-9, especially in the whole group of OSAS subjects. These data underline how strong interrelationships among some parameters of the oxidative stress, in particular those reflecting lipid peroxidation, protein oxidation and NOx, and MMP-9 are evident in OSAS subjects. All these information may be useful in the clinical practice keeping in mind the cardiovascular complications generally accompanying the obstructive sleep apnea syndrome.