Himsworth in 1939 postulated that Diabetes Mellitus type 2 (DM2) was not only an insulin deficiency state but also a cellular insulin insensitivity disease. Thirty years later, DeFronzo and Reaven demonstrated that insulin resistance (IR) preceded and predisposed for DM2 and atherosclerotic-cardiovascular-disease (ACVD). Reaven was the first to point out the relationship between IR and with hyperglycemia, dyslipidosis, and hypertension as mediators for ACVD, creating the concept of Syndrome X (SX) in 1988. WHO and, thereafter, other medical societies and medical groups, mainly ATP-III, in 2002, based on the difficulty of diagnosing IR in a simple, reliable, and inexpensive way, proposed and published the Metabolic Syndrome (MS) concept, as a group of five variables, i.e., obesity, hyperglycemia, hypertriglyceridemia, low HDL, and hypertension, as an easy clinical approximation to suspect and treat an increased cardiometabolic risk. Nowadays, there are deep and extensive controversies on this issue; however, these controversies do not really exist since all discordant points of view are rather quantitative and not qualitative in nature. This article is aimed at differentiating and harmonizing the complementary concepts of SX and MS, at analyzing why MS is a good "clinical window" to look for IR and its underlying manifestations, and finally to accept that the MS concept complements, but does not substitute or antagonize, traditional scales used to asses cardiovascular risk, such as the Framingham scale.