As other monosaccharide mimics such as the azasugars and the carbasugars (with nitrogen and carbon atom, respectively, instead of oxygen atom in the ring) the thiosugars (with sulfur atom instead of oxygen atom in the ring) have gained importance in glycobiology and as potential drugs. Biological properties of monothiosaccharides are presented and the methods for their synthesis are reviewed and analyzed. Since the report of the synthesis of 5-thio-alpha-D-xylopyranose, the first example of thiosugars ever described, forty years of imaginative chemistry have produced a large number of monothiosaccharides and of analogs of biological interest. The preparative chemists have at their disposal a panoply of methodologies relying on pure chemical or on biochemical means, using carbohydrate or non-carbo hydrate precursors. Because the sulfur moieties can participate more readily than the corresponding oxygen moieties in heterolytical processes, the chemistry of the thiosugars and their analogs is more subtile and sometimes more delicate than that of the corresponding aldoses and alditols.