[The idea of a constellation of abnormalities linked to insulin resistance as a key component was pioneered and summarized by Reaven in 1988 under the name of “X” syndrome. Based on the various elements of the syndrome, several synonyms have been proposed, including “deadly trio”, “deadly quartet”, “central fat syndrome”, “insulin resistance syndrome”. To avoid the confusion of this entity with “cardial X syndrome”, an established syndrome in cardiology, and instead of the rather long “metabolic X syndrome”, I have proposed the term “Xyndrome”. Irrespective of how it is called, this syndrome has come into the focus of clinical research; using the keyword “metabolic syndrome” to search in the index of the National Library of Medicine, 15.661 citations pop up, and in February 2006 only, 168 papers were published in this field. In spite of this, several international scientific organizations have recently claimed that metabolic syndrome has not been unambiguously defined, its diagnostic criteria are contradictory, and finally, the syndrome as an entity has no more value in predicting cardiovascular risk than the sum of its individual components has, therefore, the use of this notion in the clinical practice is not recommended. There are, however, opposing opinions emphasizing the importance of abdominal obesity - today considered to be most essential element -, data from recent research, and the didactic advantage that the use of this notion has improved complex treatment of its various components. It is crucial to understand that “syndrome” is not more - and not less, either - than a clustering of symptoms and findings, and should not be treated as a distinct disease. The emergence of the notion of metabolic syndrome, however, has been a step forward in the medical concept in that metabolic and cardiovascular diseases are now dealt with in a more complex way, which warrants the maintenance of this notion and the increase of our understanding by continuing research in this field.]