The acid catalyzed dehydration of hexoses or polysaccharides issued from biomass results in the formation of 5-hydroxymethylfurfural. After the description of mechanism of dehydration and the study of the parameters influencing the kinetic of the reaction, the specific preparations are reviewed. The chemical properties are described including different recent results obtained in our laboratory. The acid catalyzed dehydration of hexoses leads to the formation of 5-hydroxymethylfurfural (HMF). HMF has been first identified by Fenton and Gostling (1899), then some years later by Von Ekenstein (1909). This compound has been the subject of an abundant amount of papers of which the most important are quoted in about ten reviews. In the series “Advances in Carbohydrate Chemistry”, two reviews have been published, one by Newth (1951) and the other by Feather (1973). Between these two dates, Moyes (1964) has written a review which reports the preparation procedures, the physical and chemical properties and the industrial uses. In 1981, two French reviews appeared : one by Gaset (1981) concerning the HMF manufacture and the other by Faury (1981) on further HMF chemistry. More recently Kuster (1990) has written a focus on HMF manufacture covering most of the relevant data of the last thirty years. In addition, furan polymers have been reviewed by Moore and Kelly (1977) and lately by Gandini (1987). The industrial growing importance of HMF with the development of fine organic chemistry using this compound was the driving force for writing this new overview.