Thiamine tetrahydrofurfuryl disulfide (TTFD) is the synthetic counterpart of allithiamine, occurring naturally in garlic. Allithiamine was discovered in Japan in 1951. Its extensive research was reported by a group known as the Vitamin B Research Committee of Japan, and given this name because of its existence in the bulbs of many of the allium species of plants. It was found to be a disulfide derivative of thiamine, produced as a result of enzymatic action on the thiamine molecule in garlic bulbs when the bulb is cut or crushed. Subsequent experimental work in both animals and human subjects revealed that its metabolic effect was much more powerful than the thiamine from which it was derived. Japanese investigators created a number of synthetic forms and investigated their use in a number of human disease conditions. Although some derivatives have been synthesized without a disulfide bond in the molecule, these investigators emphasized that the disulfide was an extremely important part of its biologic action and TTFD is the most modern of the disulfide derivatives. Because at least part of its beneficial effects are the same as water soluble thiamine salts, this review deals first with the clinical uses of thiamine (vitamin B1) in medicine.