The vibrational spectrum of the pyridinium ion, C5H5NH+, and the N-deuterated species has been studied in several pyridinium salts. By comparison with benzene and deuterobenzene (with which the pyridinium ion is isoelectronic) a fairly complete assignment has been made. The N—H bonds, which are hydrogen bonded to the anions, have stretching vibrations which show systematic variations depending on the nature of the anion. The N—H in-plane deformation vibrations show little variation while the out-of-plane deformation vibrations, some of which do vary, are probably affected, in addition, by other factors.