Publisher Summary This chapter attempts to cover several kinds of heterocycles containing the sulfamide moiety. Earlier reports dealt with cyclic sulfamides, and with the chemistry of thiadiazole and thiadiazine S-oxides. These compounds have also been mentioned in Comprehensive Heterocyclic Chemistry. There has been extensive work on the chemistry and reactions of sulfamide and of alkylsulfamoyl chlorides that include heterocycles of this kind. This chapter offers a more extensive scope, since it covers some aspects of thiadiazines and thiadiazoles, such as tautomerism and aromaticity that had not previously been dealt with. It also includes other heterocycles. This article has been divided on the basis of the nature and size of the heterocyclic ring. The size of the rings range from three- to nine-membered heterocycles, although a ring with 30 members has also been described. A variety of biological activities are reported for different heterocycles containing the sulfamide moiety. For the sake of brevity, they are listed together with their respective structures.