The synthesis, X-ray structure, and the magnetic properties of 2-(2-methyl-1,3-propanediol)-4,4,5,5-tetramethyl-3-oxylimidazoline 1-oxide are described. The nitronyl nitroxide packs in stacks of dimers. Two CH2O-H...O-N hydrogen bonds and one CH2OH group of each nitronyl nitroxide link two mols. into a dimer. The addnl. CH2OH group in each mol. forms CH2O-H...O-N hydrogen bonds to a second dimer and so on, leading finally to columns of dimers. Each column is surrounded by six other columns. The magnetic behavior of the crystal is strongly temp. dependent, evidence for intermol. interactions between the mols. at room temp. DFT calcns. support an antiferromagnetic coupling of nitronyl nitroxide mols. in the dimer.