1-Methyluracil is of special importance in biochemistry, since uracil attaches ribose in ribonucleic acid (RNA) just precisely at the N1 atom. H-bond complex formation between 1-methyluracil and glycine has been investigated by theoretical calculations and FT-IR spectroscopy in Ar matrices. It forms 1:1 complexes with 9-ethyl-8-bromo-2,6-diaminopurine and the complex structure has been determined by three-dimensional X-ray diffraction methods.