In this paper, we report a novel synthesis of anhydrous 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-H). An X-ray crystal structure and full characterization of the compound are included. Compared to hydrated TEMPO-H, its anhydrous form exhibits improved stability and a differing chemical reactivity. The reactions of anhydrous TEMPO-H with a variety of low-valent carbon centres are described. For example, anhydrous TEMPO-H was reacted with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), an unsaturated NHC. Crystals of [CHNC 6 H 2 (CH 3 ) 3 ] 2 C ◊ ◊ ◊ HO-(NC 5 H 6 (CH 3 ) 4 ), IMes ◊ ◊ ◊ TEMPO-H, were isolated and a crystal structure determined. The experimental structure is compared to the results of theoretical calculations on the hydrogen-bonded dimer. Anhydrous TEMPO-H was also reacted with the saturated NHC, 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr), giving the product [CH 2 Ni-Pr 2 C 6 H 3 ] 2 CH ◊ ◊ ◊ O(NC 5 H 6 (CH 3 ) 4 ). In contrast, the reaction of hydrated TEMPO-H with 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene gave small amounts of the hydrolysis product, N-(2,6-diisopropylphenyl)-N- [2-(2,6-diisopropylphenylamino)ethyl]formamide. Finally, anhydrous TEMPO-H was reacted with (triphenylphosphoranylidene)ketene to generate Ph 3 PC(H)C( O)O(NC 5 H 6 (CH 3 ) 4 ). A full characterization of the product, including an X-ray crystal structure, is described. Scheme 1 Structural isomers formed by the reaction of TEMPO-H (1) with NHCs (2).Access to anhydrous TEMPO-H has not been reported in the literature, but it was clear to us early on that the water in