In this study, we evaluated lipid peroxidation, expressed as TBARS, nitric oxide metabolites (NOx), and their ratio (TBARS/NOx) in a group of MS subjects subdivided according to the presence or not of diabetes mellitus and also according to the degree of insulin resistance, expressed as triglycerides/HDL-cholesterol (TG/HDL-C) index; this index, in fact, may be considered an indicator of insulin resistance [33–35] its logarithm being inversely correlated with insulin sensitivity measures, such as the homeostasis model assessment and the quantitative insulin sensitivity check index [36]. Here, INS is linked to diabetes mellitus.