A new nitronyl nitroxide radical, 2-(3-quinolyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxide, is found to exhibit a ferromagnetic intermolecular interaction with a Weiss constant THETA = 0.27 K. The crystal structure is described and the relationship with the intermolecular interaction is discussed.