Abstract: In this paper an improved procedure on the oxidation of 4-oxo-2,2,6,6-tetramethylpiperidine to 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl is described.The improved method gave high yields of the radical product within a much shortened time.The reaction between 4-oxo-2,2,6,6-tetramethylpiperidine-l-oxyl with hydroxylamine hydrochloride under different pHconditions was studied.It was found that under basic conditions (pH 9-11),the oxime of the radical was obtained,under neutral conditions (pH 7-8),the Beckmann rearrangement product of the oxime was obtained,while under acidic conditions (pH 2-5),a nonradical product was obtained in the form of a hydrochloride which had the molecular formula of C₉H₁₈N₂O₂·HCl.4-oxo-2,2,6,6-tetramethylpiperidine-l-oxyl could be readily reduced by ascorbic acid to the corresponding hydroxylamine.The electron spin resonance spectra of the nitroxides in the solid state and their mass spectra were recorded.