The syntheses of 4-amino-thiomorpholine-1,1-dioxide (12) and 4-hydroxythiomorpholine-1,1-dioxide (11) from 1,4-thioxane-1,1-dioxide (1) by pressureless reaction of1with hydrazine hydrate and hydroxylamine, resp. is described. In analogy various other N-substituted thiomorpholine-1,1-dioxides are obtained with prim. amines (2–8) and diamines (9, 10).12condensates with aldehydes (14–24) and ketones (25–29); reaction of12with1gives N,N′-dithiomorpholine-1,1-dioxide (13). Acylation of12with monochlorides (30–35), dichlorides of dicarboxylic acids (36–40) and carboxylic acid anhydrides (41–43) proceeds smoothly. Compounds38–43are cyclic imides. Isocyanates give with12the expected compounds45–48.12reacts with chlorinated 1,3,5-triazines to compounds which can be purified only with difficulty (49–51). Quaternization of the N-substituted thiomorpholine-1,1-dioxides with benzylbromide (52, 53) and methyliodide (54, 55) is possible. Ethylenbromide reacts with9to give the bis quaternization product56. Further reactions of thiomorpholine-1,1-dioxide (57) with sulfuryl chloride (58), bromo cyanide (59), allylic chloride (60), chloro acetonitrile (61) and trityl chloride (62) are described.11reacts with carboxylic acid chlorides (63–65) and iso-cyanates (66–70) to yield the expected compounds. Propylene oxide gives with12the addition product71; sulfur dioxide is added to11to thiomorpholine-1,1-dio