The infra-red spectra of o-nitroanilines do not indicate any intramolecular hydrogen bonding unless there are nitro groups in both positions 2 and 6 to the amino group. An examination of the literature shows that there is no unambiguous evidence from other sources of such bonding in simple o-nitroanilines. An explanation is given of the variation of the stretching frequencies of the nitro group in sterically hindered compounds and in those with electron-donating ortho- and para-substituents.