The neutral imino-semiquinone, 4,6-di-tert-butyl-2-tert-butylimino-semiquinone (isqH(center dot)), can be prepared by a conproportionation of the parent aminophenol and iminoquinone compounds. The neutral radical species has been characterized in the solid state by X-ray diffraction and in solution by EPR and UV-vis absorption spectroscopy. The stability of the open-shell radical is derived from the basicity of the terf-butylimino group and the intramolecular hydrogen bond.