In order to further elucidate the properties and biological behavior of 5-hydroxy-2-hydroxymethyl-1-methylpyrid-4-one (M1), its X-ray structure has been determined, and the ability of its gadolinium complex to enhance the relaxation of 13C nuclei has been examined. X-ray analysis using Mo K alpha radiation shows that M1 crystallizes in the monoclinic space group C2/c with a complex intermolecular array of hydrogen bonding. No water molecules were present within the unit cell. Gd(M1)2NO3 x 3H2O has been prepared and found to be very soluble in water. The effect of low concentrations of Gd(III) on enhancing the 13C relaxation times of M1 was examined. Trace amounts of Gd(NO3)3 x 6H2O resulted in significant decreases in the relaxation time of certain carbon atoms relative to the control measurements, and these data indicate that carbon atoms which bear donor atoms for Gd(III) undergo a significantly greater relaxation than the other carbons. The water solubility and hydrophilic character of this complex suggest that it may prove useful for the determination of metal binding sites on peptides and oligonucleotides.