The spectra of pyridine and 33 substituted pyridines are compared to establish correlations of the absorption bands with the molecular structure of the compounds. Five groups of compounds are considered, namely, 2-, 3- and 4-monosubstituted, and di- and tri-substituted types. Absorption bands that are generally characteristic of an alkylpyridine system are found near 1600, 1570 and 1000 cm/sup -1/. For 3-alkylpyridines and 2,5-dialkylpyridines, the latter peak is removed to 1021 to 1034 cm/sup -1/. Peaks in the regions 1280 to 1330 cm/sup -1/ and 1222 to 1253 cm/sup -1/ are strong confirmatory evidence for the alkylpyridine system. The separation of the absorption bands near 1600 and 1570 cm/sup -1/ is approximately 40 cm/sup -1/ for 4-monoalkylpyridines and 20 cm/sup -1/ for the other two types of monosubstituted pyridines. The 4-monosubstituted pyridines also have a band in the region 1067 to 1072 cm/sup -1/. The 2-monosubstituted pyridines have bands at 1050 cm/sup -1/ and in the region 1146 to 1152 cm/sup -1/. The 3-monosubstituted pyridines have bands at 1117 to 1131 cm/sup -1/ and 1180 to 1196 cm/sup -1/. Disubstituted pyridines all have a peak in the region 1099 to 1136 cm/sup -1/. No correlations were found in this region for trisubstituted pyridines. Out-of-plane deformation vibrations for 2-monoalkylpyridines were found in the region 743 to 750 cm/sup -1/; for 3-monoalkylpyridines at 789 to 810 cm/sup -1/ and 712 to 715 cm/sup -1/; for 4-monoalkylpyridines at 785 to 822 cm/sup -1/; for disubstituted pyridines at 816 to 833 cm/sup -1/ and 725 to 743 cm/sup -1/; and for trisubstituted pyridines at 724 to 732 cm/sup -1/. For monoalkylpyridines the relative intensity and location of absorption bands in the 1667 to 2080 cm/sup -1/ region differ only if the position of substitution differs. Typical absorption patterns in the region are given for 2-, 3- and 4-monoalkylpyridines. Patterns are also suggested for 2,3-, 2,4-, 2,5- and 2,6-disubstituted pyridines.