The infrared spectra of three derivatives of 1,3,5,8-Tetra-azanaphthalene viz., 3-Methyl-8-hydroxyethyl-lumazine, 6,7,8-Trimethyllumazine and 2-Dimethylamino-6,7-diphenylpterine have been determined in the region 400–4000 cm−1and correlated. Band assignments of these complex molecules are discussed in relation to those of naphthalene, azanaphthalenes and their derivatives. The shifs occuring in symmetric and antisymmetric stretching and symmetric deformation frequencies of C-H in methyl group when attached to the nitrogen have been examined in relation to the structure of the molecules. A strong intermolecular hydrogen bonding in 3-Methyl-8-hydroxy ethyl lumazine and 2-Dimethylamino-6,7-diphenyl pterine has been observed.